SQL join table to itself to get data for previous year

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SQL. How can I join table to itself to get desired results just as shown in the table below. The logic is that I want to have Units for the same product and corresponding month of previous year.

The simple left join on source table to itself on key a.[year]=b.[year]+1 (and of course month to month and product to product) would cause the loss of the data where we had values in the previous year and do not have now.

sql sql-server tsql join self-join

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edited yesterday

asked yesterday

Przemyslaw Remin

85632161

• 
  
  
  

  
  

  
  
  
  
  
  

  
  Why does 2017, 4, 1 has 2933?
  – Salman A
  yesterday
  
  
  

  
  
  
  


• 
  
  
  

  
  

  
  
  
  
  
  

  
  @SalmanA Corrected. Thx.
  – Przemyslaw Remin
  yesterday
  

  
  
  
  


• 
  
  
  

  
  

  
  
  
  
  
  

  
  Do you really need the rows for 2017? You could simply have an output with 5 rows like product, month, 2018_units, 2017_units
  – Salman A
  yesterday
  

  
  
  
  


• 
  
  
  

  
  

  
  
  
  
  
  

  
  @SalmanA yes, I do need the data in that structure for every year - there are more years then just 2018, and 2017.
  – Przemyslaw Remin
  23 hours ago
  

  
  
  
  

add a comment | 

up vote
2
down vote

favorite

1

SQL. How can I join table to itself to get desired results just as shown in the table below. The logic is that I want to have Units for the same product and corresponding month of previous year.

The simple left join on source table to itself on key a.[year]=b.[year]+1 (and of course month to month and product to product) would cause the loss of the data where we had values in the previous year and do not have now.

sql sql-server tsql join self-join

share|improve this question

edited yesterday

asked yesterday

Przemyslaw Remin

85632161

• 
  
  
  

  
  

  
  
  
  
  
  

  
  Why does 2017, 4, 1 has 2933?
  – Salman A
  yesterday
  
  
  

  
  
  
  


• 
  
  
  

  
  

  
  
  
  
  
  

  
  @SalmanA Corrected. Thx.
  – Przemyslaw Remin
  yesterday
  

  
  
  
  


• 
  
  
  

  
  

  
  
  
  
  
  

  
  Do you really need the rows for 2017? You could simply have an output with 5 rows like product, month, 2018_units, 2017_units
  – Salman A
  yesterday
  

  
  
  
  


• 
  
  
  

  
  

  
  
  
  
  
  

  
  @SalmanA yes, I do need the data in that structure for every year - there are more years then just 2018, and 2017.
  – Przemyslaw Remin
  23 hours ago
  

  
  
  
  

add a comment | 

up vote
2
down vote

favorite

1

up vote
2
down vote

favorite

1

1

SQL. How can I join table to itself to get desired results just as shown in the table below. The logic is that I want to have Units for the same product and corresponding month of previous year.

The simple left join on source table to itself on key a.[year]=b.[year]+1 (and of course month to month and product to product) would cause the loss of the data where we had values in the previous year and do not have now.

sql sql-server tsql join self-join

share|improve this question

edited yesterday

asked yesterday

Przemyslaw Remin

85632161

SQL. How can I join table to itself to get desired results just as shown in the table below. The logic is that I want to have Units for the same product and corresponding month of previous year.

The simple left join on source table to itself on key a.[year]=b.[year]+1 (and of course month to month and product to product) would cause the loss of the data where we had values in the previous year and do not have now.

sql sql-server tsql join self-join

sql sql-server tsql join self-join

share|improve this question

edited yesterday

asked yesterday

Przemyslaw Remin

85632161

share|improve this question

edited yesterday

asked yesterday

Przemyslaw Remin

85632161

share|improve this question

share|improve this question

edited yesterday

edited yesterday

edited yesterday

asked yesterday

Przemyslaw Remin

85632161

asked yesterday

Przemyslaw Remin

85632161

asked yesterday

Przemyslaw Remin

85632161

85632161

• 
  
  
  

  
  

  
  
  
  
  
  

  
  Why does 2017, 4, 1 has 2933?
  – Salman A
  yesterday
  
  
  

  
  
  
  


• 
  
  
  

  
  

  
  
  
  
  
  

  
  @SalmanA Corrected. Thx.
  – Przemyslaw Remin
  yesterday
  

  
  
  
  


• 
  
  
  

  
  

  
  
  
  
  
  

  
  Do you really need the rows for 2017? You could simply have an output with 5 rows like product, month, 2018_units, 2017_units
  – Salman A
  yesterday
  

  
  
  
  


• 
  
  
  

  
  

  
  
  
  
  
  

  
  @SalmanA yes, I do need the data in that structure for every year - there are more years then just 2018, and 2017.
  – Przemyslaw Remin
  23 hours ago
  

  
  
  
  

add a comment | 

• 
  
  
  

  
  

  
  
  
  
  
  

  
  Why does 2017, 4, 1 has 2933?
  – Salman A
  yesterday
  
  
  

  
  
  
  


• 
  
  
  

  
  

  
  
  
  
  
  

  
  @SalmanA Corrected. Thx.
  – Przemyslaw Remin
  yesterday
  

  
  
  
  


• 
  
  
  

  
  

  
  
  
  
  
  

  
  Do you really need the rows for 2017? You could simply have an output with 5 rows like product, month, 2018_units, 2017_units
  – Salman A
  yesterday
  

  
  
  
  


• 
  
  
  

  
  

  
  
  
  
  
  

  
  @SalmanA yes, I do need the data in that structure for every year - there are more years then just 2018, and 2017.
  – Przemyslaw Remin
  23 hours ago
  

  
  
  
  

Why does 2017, 4, 1 has 2933?
– Salman A
yesterday

Why does 2017, 4, 1 has 2933?
– Salman A
yesterday

@SalmanA Corrected. Thx.
– Przemyslaw Remin
yesterday

@SalmanA Corrected. Thx.
– Przemyslaw Remin
yesterday

Do you really need the rows for 2017? You could simply have an output with 5 rows like product, month, 2018_units, 2017_units
– Salman A
yesterday

Do you really need the rows for 2017? You could simply have an output with 5 rows like product, month, 2018_units, 2017_units
– Salman A
yesterday

@SalmanA yes, I do need the data in that structure for every year - there are more years then just 2018, and 2017.
– Przemyslaw Remin
23 hours ago

@SalmanA yes, I do need the data in that structure for every year - there are more years then just 2018, and 2017.
– Przemyslaw Remin
23 hours ago

add a comment | 

5 Answers
5

active

oldest

votes

up vote
3
down vote

A full join should be sufficient

  select distinct

    coalesce(a.year, b.year+1) as year

    , coalesce(a.month, b.month) as month

    , coalesce(a.product, b.product) as product

    , a.units as units

    , b.units as units_prev

  from yourtable a

  full join yourtable b on a.[year] = b.[year]+1 and a.[month] = b.[month] and a.product = b.product

Your expected results though are slightly off from the description 2018, month 2, product 2 does not exist with a prior value of 2933.

DB Fiddle : https://dbfiddle.uk/?rdbms=sqlserver_2017&fiddle=d01dc5bd626854b083be0864f2d5b0e4

Result :

year    month   product units   units_prev

2017    1       1       1721    

2017    2       1       4915    

2017    4       2       2933    

2017    5       1       5230    

2018    1       1               1721

2018    1       2       7672    

2018    2       1       5216    4915

2018    3       1       8911    

2018    4       2               2933

2018    5       1               5230

2019    1       2               7672

2019    2       1               5216

2019    3       1               8911

If you need to filter out futures like that, then you can add an additional where predicate, something like :

where coalesce(a.year, b.year+1) <= year(getdate())

share|improve this answer

edited yesterday

answered yesterday

Andrew

21.8k35279

• 
  
  
  

  
  

  
  
  
  
  
  

  
  Surprising! You do not join on [month]? Is that so or you forgot about it?
  – Przemyslaw Remin
  yesterday
  

  
  
  
  


• 
  
  
  

  
  

  
  
  
  
  
  

  
  Forgot during edits :)
  – Andrew
  yesterday
  

  
  
  
  


• 
  
  
  

  
  

  
  
  
  
  
  

  
  ok, what was catching me out was the coalesce of the year, it should of had b,year+1 - technically, in 2019, month 3 for product 1 there is a units_prev of 8911 - but you don't give it in your expected results
  – Andrew
  yesterday
  

  
  
  
  


• 
  
  
  

  
  

  
  
  
  
  
  

  
  yeap, you are right. I corrected it.
  – Przemyslaw Remin
  yesterday
  

  
  
  
  

add a comment | 

up vote
2
down vote

year month

Use cross join to generate the rows, left join to bring in the data and then lag() to get the "previous" value:

select y.year, m.month, p.product, t.units,

       lag(t.units) over (partition by p.product, m.month order by y.year) as prev_units

from (select distinct year from t) y cross join

     (select distinct month from t) m cross join

     (select distinct product from t) p left join

     t

     on t.year = y.year and t.month = m.month and t.product = p.producct;

share|improve this answer

edited yesterday

answered yesterday

Gordon Linoff

744k32285390

• 
  
  
  

  
  

  
  
  
  
  
  

  
  I like its simplicity but it should be improved. It produces three nulls in the product column on my data. In my expected results there should be no rows for the months of the product 2 where there is no sales in neither 2017 and 2018. I think your Cartesian would produce rows for that. Can you please put aliases in the second line of your code?
  – Przemyslaw Remin
  yesterday
  
  
  

  
  
  
  


• 
  
  
  

  
  

  
  
  
  
  
  

  
  @PrzemyslawRemin . . . Yes, I see that you also want the product to be cross joined as well. The query is fixed.
  – Gordon Linoff
  yesterday
  

  
  
  
  


• 
  
  
  

  
  

  
  
  
  
  
  

  
  From the expected results shown, I gather they are rather looking for (select distinct year from t) y cross join (select distinct month, product from t) mp.
  – Thorsten Kettner
  yesterday
  
  
  

  
  
  
  


• 
  
  
  

  
  

  
  
  
  
  
  

  
  @GordonLinoff Almost done. Is additional where coalesce(units,prev_units) is not null the best way to get your query to desired results? I do not want the rows where there are no sales for this and previous year. The are some products that have sales only in specific months of the year. Since source table is couple of milion rows I do not want the weeds at once if possible.
  – Przemyslaw Remin
  yesterday
  

  
  
  
  


• 
  
  
  

  
  

  
  
  
  
  
  

  
  @PrzemyslawRemin . . . Yes, I think that will do it.
  – Gordon Linoff
  yesterday
  

  
  
  
  

 | 
show 2 more comments

up vote
1
down vote

I would go with LAG, and a calendar table.

SELECT C.[Year],

       C.[Month],

       YPT.product,

       YST.units,

       YST.LAG(YST.units) OVER (PARTITION BY YTP.[product],C.[month] ORDER BY C.[year]) AS UnitsPrev

FROM CalendarTable C

     CROSS JOIN YourProductTable YPT

     LEFT JOIN YourSourceTable YST ON C.[Year] YST.[Year]

                                  AND C.[Month] = YST.[Month]

                                  AND YPT.Product = YST.Product

WHERE C.[day] = 1

  AND C.[date] BETWEEN {SomeStartDate} AND {SomeEndDate];

This guessing a little on your design (it assumes you have a product table).

share|improve this answer

edited yesterday

answered yesterday

Larnu

13.4k31329

• 
  
  
  

  
  1
  

  
  
  
  
  
  

  
  I do not have [Day].
  – Przemyslaw Remin
  yesterday
  

  
  
  
  


• 
  
  
  

  
  

  
  
  
  
  
  

  
  @PrzemyslawRemin C.[Day] = 1 not YST.[Day]
  – Larnu
  yesterday
  

  
  
  
  


• 
  
  
  

  
  

  
  
  
  
  
  

  
  If, however, you mean that your Calendar Table doesn't have a day column, @PrzemyslawRemin my question is why? That's a very important column to have in your calendar table, and I would suggest you make changes to it to include it.
  – Larnu
  yesterday
  
  
  

  
  
  
  


• 
  
  
  

  
  

  
  
  
  
  
  

  
  I do not have [Day] column. Simply because I work on monthly data. My [Units] column is aggregated to full months.
  – Przemyslaw Remin
  yesterday
  
  
  

  
  
  
  


• 
  
  
  

  
  

  
  
  
  
  
  

  
  So, @PrzemyslawRemin ,in your calendar table, are you only storing the first day of the month? If so, then just remove AND C.[Day] = 1 from the ON clause. If not, then why isn't day in your calendar table if your have a calendar table with every day of the month in it. However, based on your above statement, why does your calendar table NOT have every calendar day in it? That's why it's called a calendar table.
  – Larnu
  yesterday
  

  
  
  
  

 | 
show 2 more comments

up vote
1
down vote

You could generate all possible combinations for year, month and product in your data using CROSS JOIN. A simple LEFT JOIN will give you the value or NULL if data for a specific combination exists.

DECLARE @t TABLE (year int, month int, product int, unit int);

INSERT INTO @t VALUES

(2017, 1, 1, 1721),

(2017, 2, 1, 4915),

(2017, 5, 1, 5230),

(2018, 2, 1, 5216),

(2018, 3, 1, 8911),

(2017, 4, 2, 2933),

(2018, 1, 2, 7672);



SELECT ally.year, allm.month, allp.product, curr.units, prev.units AS units_prev

FROM (SELECT DISTINCT year FROM @t) AS ally

CROSS JOIN (SELECT DISTINCT product FROM @t) AS allp

CROSS JOIN (SELECT DISTINCT month FROM @t) AS allm

LEFT JOIN @t AS curr ON curr.year = ally.year AND curr.product = allp.product AND curr.month = allm.month

LEFT JOIN @t AS prev ON prev.year = ally.year - 1 AND prev.product = allp.product AND prev.month = allm.month

Result:

| year | month | product | units | units_prev |

|------|-------|---------|-------|------------|

| 2017 | 1     | 1       | 1721  | NULL       |

| 2017 | 2     | 1       | 4915  | NULL       |

| 2017 | 3     | 1       | NULL  | NULL       |

| 2017 | 4     | 1       | NULL  | NULL       |

| 2017 | 5     | 1       | 5230  | NULL       |

| 2017 | 1     | 2       | NULL  | NULL       |

| 2017 | 2     | 2       | NULL  | NULL       |

| 2017 | 3     | 2       | NULL  | NULL       |

| 2017 | 4     | 2       | 2933  | NULL       |

| 2017 | 5     | 2       | NULL  | NULL       |

| 2018 | 1     | 1       | NULL  | 1721       |

| 2018 | 2     | 1       | 5216  | 4915       |

| 2018 | 3     | 1       | 8911  | NULL       |

| 2018 | 4     | 1       | NULL  | NULL       |

| 2018 | 5     | 1       | NULL  | 5230       |

| 2018 | 1     | 2       | 7672  | NULL       |

| 2018 | 2     | 2       | NULL  | NULL       |

| 2018 | 3     | 2       | NULL  | NULL       |

| 2018 | 4     | 2       | NULL  | 2933       |

| 2018 | 5     | 2       | NULL  | NULL       |

share|improve this answer

edited 22 hours ago

answered yesterday

Salman A

171k65328413

• 
  
  
  

  
  

  
  
  
  
  
  

  
  Hi Salman, (1) you do not have [year] column in your final result. (2) I do not understand the clause WHERE year = 2018 OR year = 2018 - 1 (it means select *). (3) [Year] column values are exemplary in source table. There are [Year] as 2016, 2015.... Please do not refer to values. (4) Can you please explain how your Cartesian product produces just 10 rows instead of 20 (see. answer of Gordon Linoff)?
  – Przemyslaw Remin
  23 hours ago
  

  
  
  
  


• 
  
  
  

  
  

  
  
  
  
  
  

  
  Sorry I thought we're talking about two years only. It could be made to work with n years easily but LAG is better than two LEFT JOINS.
  – Salman A
  23 hours ago
  
  
  

  
  
  
  


• 
  
  
  

  
  

  
  
  
  
  
  

  
  Why do you think LAG is better then two LEFT JOINS? The performance seems to be in favor of self-join: dba.stackexchange.com/questions/158374/…
  – Przemyslaw Remin
  22 hours ago
  
  
  

  
  
  
  


• 
  
  
  

  
  

  
  
  
  
  
  

  
  It depends. But I've revised my answer nevertheless. It is now exactly the same as the other except that it uses LEFT JOIN to find previous row. Plan looks slightly better.
  – Salman A
  22 hours ago
  
  
  

  
  
  
  

add a comment | 

up vote
0
down vote

If you want the rows where nothing was sold in both 2017 and 2018 as in your desired results for March 2017 as well you need to generate out the month, year and join in the product to get the null values.

This query does it for the month and year, hopefully you should be able to add the Product as well if required

DECLARE @startMonth INT=1

DECLARE @endMonth INT=12

DECLARE @startYear INT=2017

DECLARE @endYear INT=2018

;

WITH months AS (

    SELECT @startMonth AS m

    UNION ALL

    SELECT m+1 FROM months WHERE m+1<=@endMonth

),

years AS (

    SELECT @startYear AS y

    UNION ALL

    SELECT y+1 FROM years WHERE y+1<=@endYear

),

monthYears AS (

    SELECT m, y

    FROM months, years

)

SELECT  thisYear.[Year], thisYear.[Month], thisYear.[Product], thisYear.[Units], prevYear.[Units] as units_prev

FROM 

    (SELECT [Product], my.y as [Year], my.m as [Month], [Units]

    FROM monthYears my

    LEFT JOIN sales on my.m = [Month] and my.y = [Year]) as thisYear

LEFT OUTER JOIN     

    (SELECT [Product], my.y as [Year], my.m as [Month], my.y + 1 as NextYear, [Units]

    FROM monthYears my

    LEFT JOIN sales on my.m = [Month] and my.y = [Year])  as prevYear 

    on thisYear.Product = prevYear.Product

        and (thisYEAR.[Year]) = prevYear.[NextYear]

        and thisYEAR.[Month] = prevYear.[Month]

ORDER BY thisYear.[Year], thisYear.[Month], thisYear.[Product] 

option (maxrecursion 12);

share|improve this answer

answered yesterday

PhilS

1264

add a comment | 

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5 Answers
5

active

oldest

votes

5 Answers
5

active

oldest

votes

active

oldest

votes

active

oldest

votes

up vote
3
down vote

A full join should be sufficient

  select distinct

    coalesce(a.year, b.year+1) as year

    , coalesce(a.month, b.month) as month

    , coalesce(a.product, b.product) as product

    , a.units as units

    , b.units as units_prev

  from yourtable a

  full join yourtable b on a.[year] = b.[year]+1 and a.[month] = b.[month] and a.product = b.product

Your expected results though are slightly off from the description 2018, month 2, product 2 does not exist with a prior value of 2933.

DB Fiddle : https://dbfiddle.uk/?rdbms=sqlserver_2017&fiddle=d01dc5bd626854b083be0864f2d5b0e4

Result :

year    month   product units   units_prev

2017    1       1       1721    

2017    2       1       4915    

2017    4       2       2933    

2017    5       1       5230    

2018    1       1               1721

2018    1       2       7672    

2018    2       1       5216    4915

2018    3       1       8911    

2018    4       2               2933

2018    5       1               5230

2019    1       2               7672

2019    2       1               5216

2019    3       1               8911

If you need to filter out futures like that, then you can add an additional where predicate, something like :

where coalesce(a.year, b.year+1) <= year(getdate())

share|improve this answer

edited yesterday

answered yesterday

Andrew

21.8k35279

• 
  
  
  

  
  

  
  
  
  
  
  

  
  Surprising! You do not join on [month]? Is that so or you forgot about it?
  – Przemyslaw Remin
  yesterday
  

  
  
  
  


• 
  
  
  

  
  

  
  
  
  
  
  

  
  Forgot during edits :)
  – Andrew
  yesterday
  

  
  
  
  


• 
  
  
  

  
  

  
  
  
  
  
  

  
  ok, what was catching me out was the coalesce of the year, it should of had b,year+1 - technically, in 2019, month 3 for product 1 there is a units_prev of 8911 - but you don't give it in your expected results
  – Andrew
  yesterday
  

  
  
  
  


• 
  
  
  

  
  

  
  
  
  
  
  

  
  yeap, you are right. I corrected it.
  – Przemyslaw Remin
  yesterday
  

  
  
  
  

add a comment | 

up vote
3
down vote

A full join should be sufficient

  select distinct

    coalesce(a.year, b.year+1) as year

    , coalesce(a.month, b.month) as month

    , coalesce(a.product, b.product) as product

    , a.units as units

    , b.units as units_prev

  from yourtable a

  full join yourtable b on a.[year] = b.[year]+1 and a.[month] = b.[month] and a.product = b.product

Your expected results though are slightly off from the description 2018, month 2, product 2 does not exist with a prior value of 2933.

DB Fiddle : https://dbfiddle.uk/?rdbms=sqlserver_2017&fiddle=d01dc5bd626854b083be0864f2d5b0e4

Result :

year    month   product units   units_prev

2017    1       1       1721    

2017    2       1       4915    

2017    4       2       2933    

2017    5       1       5230    

2018    1       1               1721

2018    1       2       7672    

2018    2       1       5216    4915

2018    3       1       8911    

2018    4       2               2933

2018    5       1               5230

2019    1       2               7672

2019    2       1               5216

2019    3       1               8911

If you need to filter out futures like that, then you can add an additional where predicate, something like :

where coalesce(a.year, b.year+1) <= year(getdate())

share|improve this answer

edited yesterday

answered yesterday

Andrew

21.8k35279

• 
  
  
  

  
  

  
  
  
  
  
  

  
  Surprising! You do not join on [month]? Is that so or you forgot about it?
  – Przemyslaw Remin
  yesterday
  

  
  
  
  


• 
  
  
  

  
  

  
  
  
  
  
  

  
  Forgot during edits :)
  – Andrew
  yesterday
  

  
  
  
  


• 
  
  
  

  
  

  
  
  
  
  
  

  
  ok, what was catching me out was the coalesce of the year, it should of had b,year+1 - technically, in 2019, month 3 for product 1 there is a units_prev of 8911 - but you don't give it in your expected results
  – Andrew
  yesterday
  

  
  
  
  


• 
  
  
  

  
  

  
  
  
  
  
  

  
  yeap, you are right. I corrected it.
  – Przemyslaw Remin
  yesterday
  

  
  
  
  

add a comment | 

up vote
3
down vote

up vote
3
down vote

A full join should be sufficient

  select distinct

    coalesce(a.year, b.year+1) as year

    , coalesce(a.month, b.month) as month

    , coalesce(a.product, b.product) as product

    , a.units as units

    , b.units as units_prev

  from yourtable a

  full join yourtable b on a.[year] = b.[year]+1 and a.[month] = b.[month] and a.product = b.product

Your expected results though are slightly off from the description 2018, month 2, product 2 does not exist with a prior value of 2933.

DB Fiddle : https://dbfiddle.uk/?rdbms=sqlserver_2017&fiddle=d01dc5bd626854b083be0864f2d5b0e4

Result :

year    month   product units   units_prev

2017    1       1       1721    

2017    2       1       4915    

2017    4       2       2933    

2017    5       1       5230    

2018    1       1               1721

2018    1       2       7672    

2018    2       1       5216    4915

2018    3       1       8911    

2018    4       2               2933

2018    5       1               5230

2019    1       2               7672

2019    2       1               5216

2019    3       1               8911

If you need to filter out futures like that, then you can add an additional where predicate, something like :

where coalesce(a.year, b.year+1) <= year(getdate())

share|improve this answer

edited yesterday

answered yesterday

Andrew

21.8k35279

A full join should be sufficient

  select distinct

    coalesce(a.year, b.year+1) as year

    , coalesce(a.month, b.month) as month

    , coalesce(a.product, b.product) as product

    , a.units as units

    , b.units as units_prev

  from yourtable a

  full join yourtable b on a.[year] = b.[year]+1 and a.[month] = b.[month] and a.product = b.product

Your expected results though are slightly off from the description 2018, month 2, product 2 does not exist with a prior value of 2933.

DB Fiddle : https://dbfiddle.uk/?rdbms=sqlserver_2017&fiddle=d01dc5bd626854b083be0864f2d5b0e4

Result :

year    month   product units   units_prev

2017    1       1       1721    

2017    2       1       4915    

2017    4       2       2933    

2017    5       1       5230    

2018    1       1               1721

2018    1       2       7672    

2018    2       1       5216    4915

2018    3       1       8911    

2018    4       2               2933

2018    5       1               5230

2019    1       2               7672

2019    2       1               5216

2019    3       1               8911

If you need to filter out futures like that, then you can add an additional where predicate, something like :

where coalesce(a.year, b.year+1) <= year(getdate())

share|improve this answer

edited yesterday

answered yesterday

Andrew

21.8k35279

share|improve this answer

share|improve this answer

edited yesterday

edited yesterday

edited yesterday

answered yesterday

Andrew

21.8k35279

answered yesterday

Andrew

21.8k35279

answered yesterday

Andrew

21.8k35279

21.8k35279

• 
  
  
  

  
  

  
  
  
  
  
  

  
  Surprising! You do not join on [month]? Is that so or you forgot about it?
  – Przemyslaw Remin
  yesterday
  

  
  
  
  


• 
  
  
  

  
  

  
  
  
  
  
  

  
  Forgot during edits :)
  – Andrew
  yesterday
  

  
  
  
  


• 
  
  
  

  
  

  
  
  
  
  
  

  
  ok, what was catching me out was the coalesce of the year, it should of had b,year+1 - technically, in 2019, month 3 for product 1 there is a units_prev of 8911 - but you don't give it in your expected results
  – Andrew
  yesterday
  

  
  
  
  


• 
  
  
  

  
  

  
  
  
  
  
  

  
  yeap, you are right. I corrected it.
  – Przemyslaw Remin
  yesterday
  

  
  
  
  

add a comment | 

• 
  
  
  

  
  

  
  
  
  
  
  

  
  Surprising! You do not join on [month]? Is that so or you forgot about it?
  – Przemyslaw Remin
  yesterday
  

  
  
  
  


• 
  
  
  

  
  

  
  
  
  
  
  

  
  Forgot during edits :)
  – Andrew
  yesterday
  

  
  
  
  


• 
  
  
  

  
  

  
  
  
  
  
  

  
  ok, what was catching me out was the coalesce of the year, it should of had b,year+1 - technically, in 2019, month 3 for product 1 there is a units_prev of 8911 - but you don't give it in your expected results
  – Andrew
  yesterday
  

  
  
  
  


• 
  
  
  

  
  

  
  
  
  
  
  

  
  yeap, you are right. I corrected it.
  – Przemyslaw Remin
  yesterday
  

  
  
  
  

Surprising! You do not join on [month]? Is that so or you forgot about it?
– Przemyslaw Remin
yesterday

Surprising! You do not join on [month]? Is that so or you forgot about it?
– Przemyslaw Remin
yesterday

Forgot during edits :)
– Andrew
yesterday

Forgot during edits :)
– Andrew
yesterday

ok, what was catching me out was the coalesce of the year, it should of had b,year+1 - technically, in 2019, month 3 for product 1 there is a units_prev of 8911 - but you don't give it in your expected results
– Andrew
yesterday

ok, what was catching me out was the coalesce of the year, it should of had b,year+1 - technically, in 2019, month 3 for product 1 there is a units_prev of 8911 - but you don't give it in your expected results
– Andrew
yesterday

yeap, you are right. I corrected it.
– Przemyslaw Remin
yesterday

yeap, you are right. I corrected it.
– Przemyslaw Remin
yesterday

add a comment | 

up vote
2
down vote

year month

Use cross join to generate the rows, left join to bring in the data and then lag() to get the "previous" value:

select y.year, m.month, p.product, t.units,

       lag(t.units) over (partition by p.product, m.month order by y.year) as prev_units

from (select distinct year from t) y cross join

     (select distinct month from t) m cross join

     (select distinct product from t) p left join

     t

     on t.year = y.year and t.month = m.month and t.product = p.producct;

share|improve this answer

edited yesterday

answered yesterday

Gordon Linoff

744k32285390

• 
  
  
  

  
  

  
  
  
  
  
  

  
  I like its simplicity but it should be improved. It produces three nulls in the product column on my data. In my expected results there should be no rows for the months of the product 2 where there is no sales in neither 2017 and 2018. I think your Cartesian would produce rows for that. Can you please put aliases in the second line of your code?
  – Przemyslaw Remin
  yesterday
  
  
  

  
  
  
  


• 
  
  
  

  
  

  
  
  
  
  
  

  
  @PrzemyslawRemin . . . Yes, I see that you also want the product to be cross joined as well. The query is fixed.
  – Gordon Linoff
  yesterday
  

  
  
  
  


• 
  
  
  

  
  

  
  
  
  
  
  

  
  From the expected results shown, I gather they are rather looking for (select distinct year from t) y cross join (select distinct month, product from t) mp.
  – Thorsten Kettner
  yesterday
  
  
  

  
  
  
  


• 
  
  
  

  
  

  
  
  
  
  
  

  
  @GordonLinoff Almost done. Is additional where coalesce(units,prev_units) is not null the best way to get your query to desired results? I do not want the rows where there are no sales for this and previous year. The are some products that have sales only in specific months of the year. Since source table is couple of milion rows I do not want the weeds at once if possible.
  – Przemyslaw Remin
  yesterday
  

  
  
  
  


• 
  
  
  

  
  

  
  
  
  
  
  

  
  @PrzemyslawRemin . . . Yes, I think that will do it.
  – Gordon Linoff
  yesterday
  

  
  
  
  

 | 
show 2 more comments

up vote
2
down vote

year month

Use cross join to generate the rows, left join to bring in the data and then lag() to get the "previous" value:

select y.year, m.month, p.product, t.units,

       lag(t.units) over (partition by p.product, m.month order by y.year) as prev_units

from (select distinct year from t) y cross join

     (select distinct month from t) m cross join

     (select distinct product from t) p left join

     t

     on t.year = y.year and t.month = m.month and t.product = p.producct;

share|improve this answer

edited yesterday

answered yesterday

Gordon Linoff

744k32285390

• 
  
  
  

  
  

  
  
  
  
  
  

  
  I like its simplicity but it should be improved. It produces three nulls in the product column on my data. In my expected results there should be no rows for the months of the product 2 where there is no sales in neither 2017 and 2018. I think your Cartesian would produce rows for that. Can you please put aliases in the second line of your code?
  – Przemyslaw Remin
  yesterday
  
  
  

  
  
  
  


• 
  
  
  

  
  

  
  
  
  
  
  

  
  @PrzemyslawRemin . . . Yes, I see that you also want the product to be cross joined as well. The query is fixed.
  – Gordon Linoff
  yesterday
  

  
  
  
  


• 
  
  
  

  
  

  
  
  
  
  
  

  
  From the expected results shown, I gather they are rather looking for (select distinct year from t) y cross join (select distinct month, product from t) mp.
  – Thorsten Kettner
  yesterday
  
  
  

  
  
  
  


• 
  
  
  

  
  

  
  
  
  
  
  

  
  @GordonLinoff Almost done. Is additional where coalesce(units,prev_units) is not null the best way to get your query to desired results? I do not want the rows where there are no sales for this and previous year. The are some products that have sales only in specific months of the year. Since source table is couple of milion rows I do not want the weeds at once if possible.
  – Przemyslaw Remin
  yesterday
  

  
  
  
  


• 
  
  
  

  
  

  
  
  
  
  
  

  
  @PrzemyslawRemin . . . Yes, I think that will do it.
  – Gordon Linoff
  yesterday
  

  
  
  
  

 | 
show 2 more comments

up vote
2
down vote

up vote
2
down vote

year month

Use cross join to generate the rows, left join to bring in the data and then lag() to get the "previous" value:

select y.year, m.month, p.product, t.units,

       lag(t.units) over (partition by p.product, m.month order by y.year) as prev_units

from (select distinct year from t) y cross join

     (select distinct month from t) m cross join

     (select distinct product from t) p left join

     t

     on t.year = y.year and t.month = m.month and t.product = p.producct;

share|improve this answer

edited yesterday

answered yesterday

Gordon Linoff

744k32285390

year month

Use cross join to generate the rows, left join to bring in the data and then lag() to get the "previous" value:

select y.year, m.month, p.product, t.units,

       lag(t.units) over (partition by p.product, m.month order by y.year) as prev_units

from (select distinct year from t) y cross join

     (select distinct month from t) m cross join

     (select distinct product from t) p left join

     t

     on t.year = y.year and t.month = m.month and t.product = p.producct;

share|improve this answer

edited yesterday

answered yesterday

Gordon Linoff

744k32285390

share|improve this answer

share|improve this answer

edited yesterday

edited yesterday

edited yesterday

answered yesterday

Gordon Linoff

744k32285390

answered yesterday

Gordon Linoff

744k32285390

answered yesterday

Gordon Linoff

744k32285390

744k32285390

• 
  
  
  

  
  

  
  
  
  
  
  

  
  I like its simplicity but it should be improved. It produces three nulls in the product column on my data. In my expected results there should be no rows for the months of the product 2 where there is no sales in neither 2017 and 2018. I think your Cartesian would produce rows for that. Can you please put aliases in the second line of your code?
  – Przemyslaw Remin
  yesterday
  
  
  

  
  
  
  


• 
  
  
  

  
  

  
  
  
  
  
  

  
  @PrzemyslawRemin . . . Yes, I see that you also want the product to be cross joined as well. The query is fixed.
  – Gordon Linoff
  yesterday
  

  
  
  
  


• 
  
  
  

  
  

  
  
  
  
  
  

  
  From the expected results shown, I gather they are rather looking for (select distinct year from t) y cross join (select distinct month, product from t) mp.
  – Thorsten Kettner
  yesterday
  
  
  

  
  
  
  


• 
  
  
  

  
  

  
  
  
  
  
  

  
  @GordonLinoff Almost done. Is additional where coalesce(units,prev_units) is not null the best way to get your query to desired results? I do not want the rows where there are no sales for this and previous year. The are some products that have sales only in specific months of the year. Since source table is couple of milion rows I do not want the weeds at once if possible.
  – Przemyslaw Remin
  yesterday
  

  
  
  
  


• 
  
  
  

  
  

  
  
  
  
  
  

  
  @PrzemyslawRemin . . . Yes, I think that will do it.
  – Gordon Linoff
  yesterday
  

  
  
  
  

 | 
show 2 more comments

• 
  
  
  

  
  

  
  
  
  
  
  

  
  I like its simplicity but it should be improved. It produces three nulls in the product column on my data. In my expected results there should be no rows for the months of the product 2 where there is no sales in neither 2017 and 2018. I think your Cartesian would produce rows for that. Can you please put aliases in the second line of your code?
  – Przemyslaw Remin
  yesterday
  
  
  

  
  
  
  


• 
  
  
  

  
  

  
  
  
  
  
  

  
  @PrzemyslawRemin . . . Yes, I see that you also want the product to be cross joined as well. The query is fixed.
  – Gordon Linoff
  yesterday
  

  
  
  
  


• 
  
  
  

  
  

  
  
  
  
  
  

  
  From the expected results shown, I gather they are rather looking for (select distinct year from t) y cross join (select distinct month, product from t) mp.
  – Thorsten Kettner
  yesterday
  
  
  

  
  
  
  


• 
  
  
  

  
  

  
  
  
  
  
  

  
  @GordonLinoff Almost done. Is additional where coalesce(units,prev_units) is not null the best way to get your query to desired results? I do not want the rows where there are no sales for this and previous year. The are some products that have sales only in specific months of the year. Since source table is couple of milion rows I do not want the weeds at once if possible.
  – Przemyslaw Remin
  yesterday
  

  
  
  
  


• 
  
  
  

  
  

  
  
  
  
  
  

  
  @PrzemyslawRemin . . . Yes, I think that will do it.
  – Gordon Linoff
  yesterday
  

  
  
  
  

I like its simplicity but it should be improved. It produces three nulls in the product column on my data. In my expected results there should be no rows for the months of the product 2 where there is no sales in neither 2017 and 2018. I think your Cartesian would produce rows for that. Can you please put aliases in the second line of your code?
– Przemyslaw Remin
yesterday

I like its simplicity but it should be improved. It produces three nulls in the product column on my data. In my expected results there should be no rows for the months of the product 2 where there is no sales in neither 2017 and 2018. I think your Cartesian would produce rows for that. Can you please put aliases in the second line of your code?
– Przemyslaw Remin
yesterday

@PrzemyslawRemin . . . Yes, I see that you also want the product to be cross joined as well. The query is fixed.
– Gordon Linoff
yesterday

@PrzemyslawRemin . . . Yes, I see that you also want the product to be cross joined as well. The query is fixed.
– Gordon Linoff
yesterday

From the expected results shown, I gather they are rather looking for (select distinct year from t) y cross join (select distinct month, product from t) mp.
– Thorsten Kettner
yesterday

From the expected results shown, I gather they are rather looking for (select distinct year from t) y cross join (select distinct month, product from t) mp.
– Thorsten Kettner
yesterday

@GordonLinoff Almost done. Is additional where coalesce(units,prev_units) is not null the best way to get your query to desired results? I do not want the rows where there are no sales for this and previous year. The are some products that have sales only in specific months of the year. Since source table is couple of milion rows I do not want the weeds at once if possible.
– Przemyslaw Remin
yesterday

@GordonLinoff Almost done. Is additional where coalesce(units,prev_units) is not null the best way to get your query to desired results? I do not want the rows where there are no sales for this and previous year. The are some products that have sales only in specific months of the year. Since source table is couple of milion rows I do not want the weeds at once if possible.
– Przemyslaw Remin
yesterday

@PrzemyslawRemin . . . Yes, I think that will do it.
– Gordon Linoff
yesterday

@PrzemyslawRemin . . . Yes, I think that will do it.
– Gordon Linoff
yesterday

 | 
show 2 more comments

up vote
1
down vote

I would go with LAG, and a calendar table.

SELECT C.[Year],

       C.[Month],

       YPT.product,

       YST.units,

       YST.LAG(YST.units) OVER (PARTITION BY YTP.[product],C.[month] ORDER BY C.[year]) AS UnitsPrev

FROM CalendarTable C

     CROSS JOIN YourProductTable YPT

     LEFT JOIN YourSourceTable YST ON C.[Year] YST.[Year]

                                  AND C.[Month] = YST.[Month]

                                  AND YPT.Product = YST.Product

WHERE C.[day] = 1

  AND C.[date] BETWEEN {SomeStartDate} AND {SomeEndDate];

This guessing a little on your design (it assumes you have a product table).

share|improve this answer

edited yesterday

answered yesterday

Larnu

13.4k31329

• 
  
  
  

  
  1
  

  
  
  
  
  
  

  
  I do not have [Day].
  – Przemyslaw Remin
  yesterday
  

  
  
  
  


• 
  
  
  

  
  

  
  
  
  
  
  

  
  @PrzemyslawRemin C.[Day] = 1 not YST.[Day]
  – Larnu
  yesterday
  

  
  
  
  


• 
  
  
  

  
  

  
  
  
  
  
  

  
  If, however, you mean that your Calendar Table doesn't have a day column, @PrzemyslawRemin my question is why? That's a very important column to have in your calendar table, and I would suggest you make changes to it to include it.
  – Larnu
  yesterday
  
  
  

  
  
  
  


• 
  
  
  

  
  

  
  
  
  
  
  

  
  I do not have [Day] column. Simply because I work on monthly data. My [Units] column is aggregated to full months.
  – Przemyslaw Remin
  yesterday
  
  
  

  
  
  
  


• 
  
  
  

  
  

  
  
  
  
  
  

  
  So, @PrzemyslawRemin ,in your calendar table, are you only storing the first day of the month? If so, then just remove AND C.[Day] = 1 from the ON clause. If not, then why isn't day in your calendar table if your have a calendar table with every day of the month in it. However, based on your above statement, why does your calendar table NOT have every calendar day in it? That's why it's called a calendar table.
  – Larnu
  yesterday
  

  
  
  
  

 | 
show 2 more comments

up vote
1
down vote

I would go with LAG, and a calendar table.

SELECT C.[Year],

       C.[Month],

       YPT.product,

       YST.units,

       YST.LAG(YST.units) OVER (PARTITION BY YTP.[product],C.[month] ORDER BY C.[year]) AS UnitsPrev

FROM CalendarTable C

     CROSS JOIN YourProductTable YPT

     LEFT JOIN YourSourceTable YST ON C.[Year] YST.[Year]

                                  AND C.[Month] = YST.[Month]

                                  AND YPT.Product = YST.Product

WHERE C.[day] = 1

  AND C.[date] BETWEEN {SomeStartDate} AND {SomeEndDate];

This guessing a little on your design (it assumes you have a product table).

share|improve this answer

edited yesterday

answered yesterday

Larnu

13.4k31329

• 
  
  
  

  
  1
  

  
  
  
  
  
  

  
  I do not have [Day].
  – Przemyslaw Remin
  yesterday
  

  
  
  
  


• 
  
  
  

  
  

  
  
  
  
  
  

  
  @PrzemyslawRemin C.[Day] = 1 not YST.[Day]
  – Larnu
  yesterday
  

  
  
  
  


• 
  
  
  

  
  

  
  
  
  
  
  

  
  If, however, you mean that your Calendar Table doesn't have a day column, @PrzemyslawRemin my question is why? That's a very important column to have in your calendar table, and I would suggest you make changes to it to include it.
  – Larnu
  yesterday
  
  
  

  
  
  
  


• 
  
  
  

  
  

  
  
  
  
  
  

  
  I do not have [Day] column. Simply because I work on monthly data. My [Units] column is aggregated to full months.
  – Przemyslaw Remin
  yesterday
  
  
  

  
  
  
  


• 
  
  
  

  
  

  
  
  
  
  
  

  
  So, @PrzemyslawRemin ,in your calendar table, are you only storing the first day of the month? If so, then just remove AND C.[Day] = 1 from the ON clause. If not, then why isn't day in your calendar table if your have a calendar table with every day of the month in it. However, based on your above statement, why does your calendar table NOT have every calendar day in it? That's why it's called a calendar table.
  – Larnu
  yesterday
  

  
  
  
  

 | 
show 2 more comments

up vote
1
down vote

up vote
1
down vote

I would go with LAG, and a calendar table.

SELECT C.[Year],

       C.[Month],

       YPT.product,

       YST.units,

       YST.LAG(YST.units) OVER (PARTITION BY YTP.[product],C.[month] ORDER BY C.[year]) AS UnitsPrev

FROM CalendarTable C

     CROSS JOIN YourProductTable YPT

     LEFT JOIN YourSourceTable YST ON C.[Year] YST.[Year]

                                  AND C.[Month] = YST.[Month]

                                  AND YPT.Product = YST.Product

WHERE C.[day] = 1

  AND C.[date] BETWEEN {SomeStartDate} AND {SomeEndDate];

This guessing a little on your design (it assumes you have a product table).

share|improve this answer

edited yesterday

answered yesterday

Larnu

13.4k31329

I would go with LAG, and a calendar table.

SELECT C.[Year],

       C.[Month],

       YPT.product,

       YST.units,

       YST.LAG(YST.units) OVER (PARTITION BY YTP.[product],C.[month] ORDER BY C.[year]) AS UnitsPrev

FROM CalendarTable C

     CROSS JOIN YourProductTable YPT

     LEFT JOIN YourSourceTable YST ON C.[Year] YST.[Year]

                                  AND C.[Month] = YST.[Month]

                                  AND YPT.Product = YST.Product

WHERE C.[day] = 1

  AND C.[date] BETWEEN {SomeStartDate} AND {SomeEndDate];

This guessing a little on your design (it assumes you have a product table).

share|improve this answer

edited yesterday

answered yesterday

Larnu

13.4k31329

share|improve this answer

share|improve this answer

edited yesterday

edited yesterday

edited yesterday

answered yesterday

Larnu

13.4k31329

answered yesterday

Larnu

13.4k31329

answered yesterday

Larnu

13.4k31329

13.4k31329

• 
  
  
  

  
  1
  

  
  
  
  
  
  

  
  I do not have [Day].
  – Przemyslaw Remin
  yesterday
  

  
  
  
  


• 
  
  
  

  
  

  
  
  
  
  
  

  
  @PrzemyslawRemin C.[Day] = 1 not YST.[Day]
  – Larnu
  yesterday
  

  
  
  
  


• 
  
  
  

  
  

  
  
  
  
  
  

  
  If, however, you mean that your Calendar Table doesn't have a day column, @PrzemyslawRemin my question is why? That's a very important column to have in your calendar table, and I would suggest you make changes to it to include it.
  – Larnu
  yesterday
  
  
  

  
  
  
  


• 
  
  
  

  
  

  
  
  
  
  
  

  
  I do not have [Day] column. Simply because I work on monthly data. My [Units] column is aggregated to full months.
  – Przemyslaw Remin
  yesterday
  
  
  

  
  
  
  


• 
  
  
  

  
  

  
  
  
  
  
  

  
  So, @PrzemyslawRemin ,in your calendar table, are you only storing the first day of the month? If so, then just remove AND C.[Day] = 1 from the ON clause. If not, then why isn't day in your calendar table if your have a calendar table with every day of the month in it. However, based on your above statement, why does your calendar table NOT have every calendar day in it? That's why it's called a calendar table.
  – Larnu
  yesterday
  

  
  
  
  

 | 
show 2 more comments

• 
  
  
  

  
  1
  

  
  
  
  
  
  

  
  I do not have [Day].
  – Przemyslaw Remin
  yesterday
  

  
  
  
  


• 
  
  
  

  
  

  
  
  
  
  
  

  
  @PrzemyslawRemin C.[Day] = 1 not YST.[Day]
  – Larnu
  yesterday
  

  
  
  
  


• 
  
  
  

  
  

  
  
  
  
  
  

  
  If, however, you mean that your Calendar Table doesn't have a day column, @PrzemyslawRemin my question is why? That's a very important column to have in your calendar table, and I would suggest you make changes to it to include it.
  – Larnu
  yesterday
  
  
  

  
  
  
  


• 
  
  
  

  
  

  
  
  
  
  
  

  
  I do not have [Day] column. Simply because I work on monthly data. My [Units] column is aggregated to full months.
  – Przemyslaw Remin
  yesterday
  
  
  

  
  
  
  


• 
  
  
  

  
  

  
  
  
  
  
  

  
  So, @PrzemyslawRemin ,in your calendar table, are you only storing the first day of the month? If so, then just remove AND C.[Day] = 1 from the ON clause. If not, then why isn't day in your calendar table if your have a calendar table with every day of the month in it. However, based on your above statement, why does your calendar table NOT have every calendar day in it? That's why it's called a calendar table.
  – Larnu
  yesterday
  

  
  
  
  

1

1

I do not have [Day].
– Przemyslaw Remin
yesterday

I do not have [Day].
– Przemyslaw Remin
yesterday

@PrzemyslawRemin C.[Day] = 1 not YST.[Day]
– Larnu
yesterday

@PrzemyslawRemin C.[Day] = 1 not YST.[Day]
– Larnu
yesterday

If, however, you mean that your Calendar Table doesn't have a day column, @PrzemyslawRemin my question is why? That's a very important column to have in your calendar table, and I would suggest you make changes to it to include it.
– Larnu
yesterday

If, however, you mean that your Calendar Table doesn't have a day column, @PrzemyslawRemin my question is why? That's a very important column to have in your calendar table, and I would suggest you make changes to it to include it.
– Larnu
yesterday

I do not have [Day] column. Simply because I work on monthly data. My [Units] column is aggregated to full months.
– Przemyslaw Remin
yesterday

I do not have [Day] column. Simply because I work on monthly data. My [Units] column is aggregated to full months.
– Przemyslaw Remin
yesterday

So, @PrzemyslawRemin ,in your calendar table, are you only storing the first day of the month? If so, then just remove AND C.[Day] = 1 from the ON clause. If not, then why isn't day in your calendar table if your have a calendar table with every day of the month in it. However, based on your above statement, why does your calendar table NOT have every calendar day in it? That's why it's called a calendar table.
– Larnu
yesterday

So, @PrzemyslawRemin ,in your calendar table, are you only storing the first day of the month? If so, then just remove AND C.[Day] = 1 from the ON clause. If not, then why isn't day in your calendar table if your have a calendar table with every day of the month in it. However, based on your above statement, why does your calendar table NOT have every calendar day in it? That's why it's called a calendar table.
– Larnu
yesterday

 | 
show 2 more comments

up vote
1
down vote

You could generate all possible combinations for year, month and product in your data using CROSS JOIN. A simple LEFT JOIN will give you the value or NULL if data for a specific combination exists.

DECLARE @t TABLE (year int, month int, product int, unit int);

INSERT INTO @t VALUES

(2017, 1, 1, 1721),

(2017, 2, 1, 4915),

(2017, 5, 1, 5230),

(2018, 2, 1, 5216),

(2018, 3, 1, 8911),

(2017, 4, 2, 2933),

(2018, 1, 2, 7672);



SELECT ally.year, allm.month, allp.product, curr.units, prev.units AS units_prev

FROM (SELECT DISTINCT year FROM @t) AS ally

CROSS JOIN (SELECT DISTINCT product FROM @t) AS allp

CROSS JOIN (SELECT DISTINCT month FROM @t) AS allm

LEFT JOIN @t AS curr ON curr.year = ally.year AND curr.product = allp.product AND curr.month = allm.month

LEFT JOIN @t AS prev ON prev.year = ally.year - 1 AND prev.product = allp.product AND prev.month = allm.month

Result:

| year | month | product | units | units_prev |

|------|-------|---------|-------|------------|

| 2017 | 1     | 1       | 1721  | NULL       |

| 2017 | 2     | 1       | 4915  | NULL       |

| 2017 | 3     | 1       | NULL  | NULL       |

| 2017 | 4     | 1       | NULL  | NULL       |

| 2017 | 5     | 1       | 5230  | NULL       |

| 2017 | 1     | 2       | NULL  | NULL       |

| 2017 | 2     | 2       | NULL  | NULL       |

| 2017 | 3     | 2       | NULL  | NULL       |

| 2017 | 4     | 2       | 2933  | NULL       |

| 2017 | 5     | 2       | NULL  | NULL       |

| 2018 | 1     | 1       | NULL  | 1721       |

| 2018 | 2     | 1       | 5216  | 4915       |

| 2018 | 3     | 1       | 8911  | NULL       |

| 2018 | 4     | 1       | NULL  | NULL       |

| 2018 | 5     | 1       | NULL  | 5230       |

| 2018 | 1     | 2       | 7672  | NULL       |

| 2018 | 2     | 2       | NULL  | NULL       |

| 2018 | 3     | 2       | NULL  | NULL       |

| 2018 | 4     | 2       | NULL  | 2933       |

| 2018 | 5     | 2       | NULL  | NULL       |

share|improve this answer

edited 22 hours ago

answered yesterday

Salman A

171k65328413

• 
  
  
  

  
  

  
  
  
  
  
  

  
  Hi Salman, (1) you do not have [year] column in your final result. (2) I do not understand the clause WHERE year = 2018 OR year = 2018 - 1 (it means select *). (3) [Year] column values are exemplary in source table. There are [Year] as 2016, 2015.... Please do not refer to values. (4) Can you please explain how your Cartesian product produces just 10 rows instead of 20 (see. answer of Gordon Linoff)?
  – Przemyslaw Remin
  23 hours ago
  

  
  
  
  


• 
  
  
  

  
  

  
  
  
  
  
  

  
  Sorry I thought we're talking about two years only. It could be made to work with n years easily but LAG is better than two LEFT JOINS.
  – Salman A
  23 hours ago
  
  
  

  
  
  
  


• 
  
  
  

  
  

  
  
  
  
  
  

  
  Why do you think LAG is better then two LEFT JOINS? The performance seems to be in favor of self-join: dba.stackexchange.com/questions/158374/…
  – Przemyslaw Remin
  22 hours ago
  
  
  

  
  
  
  


• 
  
  
  

  
  

  
  
  
  
  
  

  
  It depends. But I've revised my answer nevertheless. It is now exactly the same as the other except that it uses LEFT JOIN to find previous row. Plan looks slightly better.
  – Salman A
  22 hours ago
  
  
  

  
  
  
  

add a comment | 

up vote
1
down vote

You could generate all possible combinations for year, month and product in your data using CROSS JOIN. A simple LEFT JOIN will give you the value or NULL if data for a specific combination exists.

DECLARE @t TABLE (year int, month int, product int, unit int);

INSERT INTO @t VALUES

(2017, 1, 1, 1721),

(2017, 2, 1, 4915),

(2017, 5, 1, 5230),

(2018, 2, 1, 5216),

(2018, 3, 1, 8911),

(2017, 4, 2, 2933),

(2018, 1, 2, 7672);



SELECT ally.year, allm.month, allp.product, curr.units, prev.units AS units_prev

FROM (SELECT DISTINCT year FROM @t) AS ally

CROSS JOIN (SELECT DISTINCT product FROM @t) AS allp

CROSS JOIN (SELECT DISTINCT month FROM @t) AS allm

LEFT JOIN @t AS curr ON curr.year = ally.year AND curr.product = allp.product AND curr.month = allm.month

LEFT JOIN @t AS prev ON prev.year = ally.year - 1 AND prev.product = allp.product AND prev.month = allm.month

Result:

| year | month | product | units | units_prev |

|------|-------|---------|-------|------------|

| 2017 | 1     | 1       | 1721  | NULL       |

| 2017 | 2     | 1       | 4915  | NULL       |

| 2017 | 3     | 1       | NULL  | NULL       |

| 2017 | 4     | 1       | NULL  | NULL       |

| 2017 | 5     | 1       | 5230  | NULL       |

| 2017 | 1     | 2       | NULL  | NULL       |

| 2017 | 2     | 2       | NULL  | NULL       |

| 2017 | 3     | 2       | NULL  | NULL       |

| 2017 | 4     | 2       | 2933  | NULL       |

| 2017 | 5     | 2       | NULL  | NULL       |

| 2018 | 1     | 1       | NULL  | 1721       |

| 2018 | 2     | 1       | 5216  | 4915       |

| 2018 | 3     | 1       | 8911  | NULL       |

| 2018 | 4     | 1       | NULL  | NULL       |

| 2018 | 5     | 1       | NULL  | 5230       |

| 2018 | 1     | 2       | 7672  | NULL       |

| 2018 | 2     | 2       | NULL  | NULL       |

| 2018 | 3     | 2       | NULL  | NULL       |

| 2018 | 4     | 2       | NULL  | 2933       |

| 2018 | 5     | 2       | NULL  | NULL       |

share|improve this answer

edited 22 hours ago

answered yesterday

Salman A

171k65328413

• 
  
  
  

  
  

  
  
  
  
  
  

  
  Hi Salman, (1) you do not have [year] column in your final result. (2) I do not understand the clause WHERE year = 2018 OR year = 2018 - 1 (it means select *). (3) [Year] column values are exemplary in source table. There are [Year] as 2016, 2015.... Please do not refer to values. (4) Can you please explain how your Cartesian product produces just 10 rows instead of 20 (see. answer of Gordon Linoff)?
  – Przemyslaw Remin
  23 hours ago
  

  
  
  
  


• 
  
  
  

  
  

  
  
  
  
  
  

  
  Sorry I thought we're talking about two years only. It could be made to work with n years easily but LAG is better than two LEFT JOINS.
  – Salman A
  23 hours ago
  
  
  

  
  
  
  


• 
  
  
  

  
  

  
  
  
  
  
  

  
  Why do you think LAG is better then two LEFT JOINS? The performance seems to be in favor of self-join: dba.stackexchange.com/questions/158374/…
  – Przemyslaw Remin
  22 hours ago
  
  
  

  
  
  
  


• 
  
  
  

  
  

  
  
  
  
  
  

  
  It depends. But I've revised my answer nevertheless. It is now exactly the same as the other except that it uses LEFT JOIN to find previous row. Plan looks slightly better.
  – Salman A
  22 hours ago
  
  
  

  
  
  
  

add a comment | 

up vote
1
down vote

up vote
1
down vote

You could generate all possible combinations for year, month and product in your data using CROSS JOIN. A simple LEFT JOIN will give you the value or NULL if data for a specific combination exists.

DECLARE @t TABLE (year int, month int, product int, unit int);

INSERT INTO @t VALUES

(2017, 1, 1, 1721),

(2017, 2, 1, 4915),

(2017, 5, 1, 5230),

(2018, 2, 1, 5216),

(2018, 3, 1, 8911),

(2017, 4, 2, 2933),

(2018, 1, 2, 7672);



SELECT ally.year, allm.month, allp.product, curr.units, prev.units AS units_prev

FROM (SELECT DISTINCT year FROM @t) AS ally

CROSS JOIN (SELECT DISTINCT product FROM @t) AS allp

CROSS JOIN (SELECT DISTINCT month FROM @t) AS allm

LEFT JOIN @t AS curr ON curr.year = ally.year AND curr.product = allp.product AND curr.month = allm.month

LEFT JOIN @t AS prev ON prev.year = ally.year - 1 AND prev.product = allp.product AND prev.month = allm.month

Result:

| year | month | product | units | units_prev |

|------|-------|---------|-------|------------|

| 2017 | 1     | 1       | 1721  | NULL       |

| 2017 | 2     | 1       | 4915  | NULL       |

| 2017 | 3     | 1       | NULL  | NULL       |

| 2017 | 4     | 1       | NULL  | NULL       |

| 2017 | 5     | 1       | 5230  | NULL       |

| 2017 | 1     | 2       | NULL  | NULL       |

| 2017 | 2     | 2       | NULL  | NULL       |

| 2017 | 3     | 2       | NULL  | NULL       |

| 2017 | 4     | 2       | 2933  | NULL       |

| 2017 | 5     | 2       | NULL  | NULL       |

| 2018 | 1     | 1       | NULL  | 1721       |

| 2018 | 2     | 1       | 5216  | 4915       |

| 2018 | 3     | 1       | 8911  | NULL       |

| 2018 | 4     | 1       | NULL  | NULL       |

| 2018 | 5     | 1       | NULL  | 5230       |

| 2018 | 1     | 2       | 7672  | NULL       |

| 2018 | 2     | 2       | NULL  | NULL       |

| 2018 | 3     | 2       | NULL  | NULL       |

| 2018 | 4     | 2       | NULL  | 2933       |

| 2018 | 5     | 2       | NULL  | NULL       |

share|improve this answer

edited 22 hours ago

answered yesterday

Salman A

171k65328413

You could generate all possible combinations for year, month and product in your data using CROSS JOIN. A simple LEFT JOIN will give you the value or NULL if data for a specific combination exists.

DECLARE @t TABLE (year int, month int, product int, unit int);

INSERT INTO @t VALUES

(2017, 1, 1, 1721),

(2017, 2, 1, 4915),

(2017, 5, 1, 5230),

(2018, 2, 1, 5216),

(2018, 3, 1, 8911),

(2017, 4, 2, 2933),

(2018, 1, 2, 7672);



SELECT ally.year, allm.month, allp.product, curr.units, prev.units AS units_prev

FROM (SELECT DISTINCT year FROM @t) AS ally

CROSS JOIN (SELECT DISTINCT product FROM @t) AS allp

CROSS JOIN (SELECT DISTINCT month FROM @t) AS allm

LEFT JOIN @t AS curr ON curr.year = ally.year AND curr.product = allp.product AND curr.month = allm.month

LEFT JOIN @t AS prev ON prev.year = ally.year - 1 AND prev.product = allp.product AND prev.month = allm.month

Result:

| year | month | product | units | units_prev |

|------|-------|---------|-------|------------|

| 2017 | 1     | 1       | 1721  | NULL       |

| 2017 | 2     | 1       | 4915  | NULL       |

| 2017 | 3     | 1       | NULL  | NULL       |

| 2017 | 4     | 1       | NULL  | NULL       |

| 2017 | 5     | 1       | 5230  | NULL       |

| 2017 | 1     | 2       | NULL  | NULL       |

| 2017 | 2     | 2       | NULL  | NULL       |

| 2017 | 3     | 2       | NULL  | NULL       |

| 2017 | 4     | 2       | 2933  | NULL       |

| 2017 | 5     | 2       | NULL  | NULL       |

| 2018 | 1     | 1       | NULL  | 1721       |

| 2018 | 2     | 1       | 5216  | 4915       |

| 2018 | 3     | 1       | 8911  | NULL       |

| 2018 | 4     | 1       | NULL  | NULL       |

| 2018 | 5     | 1       | NULL  | 5230       |

| 2018 | 1     | 2       | 7672  | NULL       |

| 2018 | 2     | 2       | NULL  | NULL       |

| 2018 | 3     | 2       | NULL  | NULL       |

| 2018 | 4     | 2       | NULL  | 2933       |

| 2018 | 5     | 2       | NULL  | NULL       |

share|improve this answer

edited 22 hours ago

answered yesterday

Salman A

171k65328413

share|improve this answer

share|improve this answer

edited 22 hours ago

edited 22 hours ago

edited 22 hours ago

answered yesterday

Salman A

171k65328413

answered yesterday

Salman A

171k65328413

answered yesterday

Salman A

171k65328413

171k65328413

• 
  
  
  

  
  

  
  
  
  
  
  

  
  Hi Salman, (1) you do not have [year] column in your final result. (2) I do not understand the clause WHERE year = 2018 OR year = 2018 - 1 (it means select *). (3) [Year] column values are exemplary in source table. There are [Year] as 2016, 2015.... Please do not refer to values. (4) Can you please explain how your Cartesian product produces just 10 rows instead of 20 (see. answer of Gordon Linoff)?
  – Przemyslaw Remin
  23 hours ago
  

  
  
  
  


• 
  
  
  

  
  

  
  
  
  
  
  

  
  Sorry I thought we're talking about two years only. It could be made to work with n years easily but LAG is better than two LEFT JOINS.
  – Salman A
  23 hours ago
  
  
  

  
  
  
  


• 
  
  
  

  
  

  
  
  
  
  
  

  
  Why do you think LAG is better then two LEFT JOINS? The performance seems to be in favor of self-join: dba.stackexchange.com/questions/158374/…
  – Przemyslaw Remin
  22 hours ago
  
  
  

  
  
  
  


• 
  
  
  

  
  

  
  
  
  
  
  

  
  It depends. But I've revised my answer nevertheless. It is now exactly the same as the other except that it uses LEFT JOIN to find previous row. Plan looks slightly better.
  – Salman A
  22 hours ago
  
  
  

  
  
  
  

add a comment | 

• 
  
  
  

  
  

  
  
  
  
  
  

  
  Hi Salman, (1) you do not have [year] column in your final result. (2) I do not understand the clause WHERE year = 2018 OR year = 2018 - 1 (it means select *). (3) [Year] column values are exemplary in source table. There are [Year] as 2016, 2015.... Please do not refer to values. (4) Can you please explain how your Cartesian product produces just 10 rows instead of 20 (see. answer of Gordon Linoff)?
  – Przemyslaw Remin
  23 hours ago
  

  
  
  
  


• 
  
  
  

  
  

  
  
  
  
  
  

  
  Sorry I thought we're talking about two years only. It could be made to work with n years easily but LAG is better than two LEFT JOINS.
  – Salman A
  23 hours ago
  
  
  

  
  
  
  


• 
  
  
  

  
  

  
  
  
  
  
  

  
  Why do you think LAG is better then two LEFT JOINS? The performance seems to be in favor of self-join: dba.stackexchange.com/questions/158374/…
  – Przemyslaw Remin
  22 hours ago
  
  
  

  
  
  
  


• 
  
  
  

  
  

  
  
  
  
  
  

  
  It depends. But I've revised my answer nevertheless. It is now exactly the same as the other except that it uses LEFT JOIN to find previous row. Plan looks slightly better.
  – Salman A
  22 hours ago
  
  
  

  
  
  
  

Hi Salman, (1) you do not have [year] column in your final result. (2) I do not understand the clause WHERE year = 2018 OR year = 2018 - 1 (it means select *). (3) [Year] column values are exemplary in source table. There are [Year] as 2016, 2015.... Please do not refer to values. (4) Can you please explain how your Cartesian product produces just 10 rows instead of 20 (see. answer of Gordon Linoff)?
– Przemyslaw Remin
23 hours ago

Hi Salman, (1) you do not have [year] column in your final result. (2) I do not understand the clause WHERE year = 2018 OR year = 2018 - 1 (it means select *). (3) [Year] column values are exemplary in source table. There are [Year] as 2016, 2015.... Please do not refer to values. (4) Can you please explain how your Cartesian product produces just 10 rows instead of 20 (see. answer of Gordon Linoff)?
– Przemyslaw Remin
23 hours ago

Sorry I thought we're talking about two years only. It could be made to work with n years easily but LAG is better than two LEFT JOINS.
– Salman A
23 hours ago

Sorry I thought we're talking about two years only. It could be made to work with n years easily but LAG is better than two LEFT JOINS.
– Salman A
23 hours ago

Why do you think LAG is better then two LEFT JOINS? The performance seems to be in favor of self-join: dba.stackexchange.com/questions/158374/…
– Przemyslaw Remin
22 hours ago

Why do you think LAG is better then two LEFT JOINS? The performance seems to be in favor of self-join: dba.stackexchange.com/questions/158374/…
– Przemyslaw Remin
22 hours ago

It depends. But I've revised my answer nevertheless. It is now exactly the same as the other except that it uses LEFT JOIN to find previous row. Plan looks slightly better.
– Salman A
22 hours ago

It depends. But I've revised my answer nevertheless. It is now exactly the same as the other except that it uses LEFT JOIN to find previous row. Plan looks slightly better.
– Salman A
22 hours ago

add a comment | 

up vote
0
down vote

If you want the rows where nothing was sold in both 2017 and 2018 as in your desired results for March 2017 as well you need to generate out the month, year and join in the product to get the null values.

This query does it for the month and year, hopefully you should be able to add the Product as well if required

DECLARE @startMonth INT=1

DECLARE @endMonth INT=12

DECLARE @startYear INT=2017

DECLARE @endYear INT=2018

;

WITH months AS (

    SELECT @startMonth AS m

    UNION ALL

    SELECT m+1 FROM months WHERE m+1<=@endMonth

),

years AS (

    SELECT @startYear AS y

    UNION ALL

    SELECT y+1 FROM years WHERE y+1<=@endYear

),

monthYears AS (

    SELECT m, y

    FROM months, years

)

SELECT  thisYear.[Year], thisYear.[Month], thisYear.[Product], thisYear.[Units], prevYear.[Units] as units_prev

FROM 

    (SELECT [Product], my.y as [Year], my.m as [Month], [Units]

    FROM monthYears my

    LEFT JOIN sales on my.m = [Month] and my.y = [Year]) as thisYear

LEFT OUTER JOIN     

    (SELECT [Product], my.y as [Year], my.m as [Month], my.y + 1 as NextYear, [Units]

    FROM monthYears my

    LEFT JOIN sales on my.m = [Month] and my.y = [Year])  as prevYear 

    on thisYear.Product = prevYear.Product

        and (thisYEAR.[Year]) = prevYear.[NextYear]

        and thisYEAR.[Month] = prevYear.[Month]

ORDER BY thisYear.[Year], thisYear.[Month], thisYear.[Product] 

option (maxrecursion 12);

share|improve this answer

answered yesterday

PhilS

1264

add a comment | 

up vote
0
down vote

If you want the rows where nothing was sold in both 2017 and 2018 as in your desired results for March 2017 as well you need to generate out the month, year and join in the product to get the null values.

This query does it for the month and year, hopefully you should be able to add the Product as well if required

DECLARE @startMonth INT=1

DECLARE @endMonth INT=12

DECLARE @startYear INT=2017

DECLARE @endYear INT=2018

;

WITH months AS (

    SELECT @startMonth AS m

    UNION ALL

    SELECT m+1 FROM months WHERE m+1<=@endMonth

),

years AS (

    SELECT @startYear AS y

    UNION ALL

    SELECT y+1 FROM years WHERE y+1<=@endYear

),

monthYears AS (

    SELECT m, y

    FROM months, years

)

SELECT  thisYear.[Year], thisYear.[Month], thisYear.[Product], thisYear.[Units], prevYear.[Units] as units_prev

FROM 

    (SELECT [Product], my.y as [Year], my.m as [Month], [Units]

    FROM monthYears my

    LEFT JOIN sales on my.m = [Month] and my.y = [Year]) as thisYear

LEFT OUTER JOIN     

    (SELECT [Product], my.y as [Year], my.m as [Month], my.y + 1 as NextYear, [Units]

    FROM monthYears my

    LEFT JOIN sales on my.m = [Month] and my.y = [Year])  as prevYear 

    on thisYear.Product = prevYear.Product

        and (thisYEAR.[Year]) = prevYear.[NextYear]

        and thisYEAR.[Month] = prevYear.[Month]

ORDER BY thisYear.[Year], thisYear.[Month], thisYear.[Product] 

option (maxrecursion 12);

share|improve this answer

answered yesterday

PhilS

1264

add a comment | 

up vote
0
down vote

up vote
0
down vote

If you want the rows where nothing was sold in both 2017 and 2018 as in your desired results for March 2017 as well you need to generate out the month, year and join in the product to get the null values.

This query does it for the month and year, hopefully you should be able to add the Product as well if required

DECLARE @startMonth INT=1

DECLARE @endMonth INT=12

DECLARE @startYear INT=2017

DECLARE @endYear INT=2018

;

WITH months AS (

    SELECT @startMonth AS m

    UNION ALL

    SELECT m+1 FROM months WHERE m+1<=@endMonth

),

years AS (

    SELECT @startYear AS y

    UNION ALL

    SELECT y+1 FROM years WHERE y+1<=@endYear

),

monthYears AS (

    SELECT m, y

    FROM months, years

)

SELECT  thisYear.[Year], thisYear.[Month], thisYear.[Product], thisYear.[Units], prevYear.[Units] as units_prev

FROM 

    (SELECT [Product], my.y as [Year], my.m as [Month], [Units]

    FROM monthYears my

    LEFT JOIN sales on my.m = [Month] and my.y = [Year]) as thisYear

LEFT OUTER JOIN     

    (SELECT [Product], my.y as [Year], my.m as [Month], my.y + 1 as NextYear, [Units]

    FROM monthYears my

    LEFT JOIN sales on my.m = [Month] and my.y = [Year])  as prevYear 

    on thisYear.Product = prevYear.Product

        and (thisYEAR.[Year]) = prevYear.[NextYear]

        and thisYEAR.[Month] = prevYear.[Month]

ORDER BY thisYear.[Year], thisYear.[Month], thisYear.[Product] 

option (maxrecursion 12);

share|improve this answer

answered yesterday

PhilS

1264

If you want the rows where nothing was sold in both 2017 and 2018 as in your desired results for March 2017 as well you need to generate out the month, year and join in the product to get the null values.

This query does it for the month and year, hopefully you should be able to add the Product as well if required

DECLARE @startMonth INT=1

DECLARE @endMonth INT=12

DECLARE @startYear INT=2017

DECLARE @endYear INT=2018

;

WITH months AS (

    SELECT @startMonth AS m

    UNION ALL

    SELECT m+1 FROM months WHERE m+1<=@endMonth

),

years AS (

    SELECT @startYear AS y

    UNION ALL

    SELECT y+1 FROM years WHERE y+1<=@endYear

),

monthYears AS (

    SELECT m, y

    FROM months, years

)

SELECT  thisYear.[Year], thisYear.[Month], thisYear.[Product], thisYear.[Units], prevYear.[Units] as units_prev

FROM 

    (SELECT [Product], my.y as [Year], my.m as [Month], [Units]

    FROM monthYears my

    LEFT JOIN sales on my.m = [Month] and my.y = [Year]) as thisYear

LEFT OUTER JOIN     

    (SELECT [Product], my.y as [Year], my.m as [Month], my.y + 1 as NextYear, [Units]

    FROM monthYears my

    LEFT JOIN sales on my.m = [Month] and my.y = [Year])  as prevYear 

    on thisYear.Product = prevYear.Product

        and (thisYEAR.[Year]) = prevYear.[NextYear]

        and thisYEAR.[Month] = prevYear.[Month]

ORDER BY thisYear.[Year], thisYear.[Month], thisYear.[Product] 

option (maxrecursion 12);

share|improve this answer

answered yesterday

PhilS

1264

share|improve this answer

share|improve this answer

answered yesterday

PhilS

1264

answered yesterday

PhilS

1264

answered yesterday

PhilS

1264

1264

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