SQL Server - Join only when the condition is number












0















I have a table EmployeeLeave



  CREATE TABLE EmployeeLeave (

  EmployeeId INT,

  LeaveType VARCHAR()

  );


LeaveType can have numbers as well as string. 



  CREATE TABLE MST_LeaveReason (

  ReasonId INT,

  Reason VARCHAR()

  );



  SELECT * FROM EmployeeLeave EL

  LEFT JOIN MST_LeaveReason LR ON LR.ReasonId = EL.LeaveType


Above query will not work as LeaveType is not always number. I want this join to work only if the LeaveType is number. How can i implement it. Please help.



Thanks in advance.






sql sql-server join







share|improve this question























  • If your varchar is only going to have a length of 1, why not use char(1) and save the overhead of having a "variable" length?

    – Larnu
    Nov 22 '18 at 11:48













  • @Larnu: VARCHAR() is (fortunately?) not legal syntax. It's probably not shorthand for VARCHAR-with-no-length-which-is-implicitly-1 in this case.

    – Jeroen Mostert
    Nov 22 '18 at 11:51


















0















I have a table EmployeeLeave



  CREATE TABLE EmployeeLeave (

  EmployeeId INT,

  LeaveType VARCHAR()

  );


LeaveType can have numbers as well as string. 



  CREATE TABLE MST_LeaveReason (

  ReasonId INT,

  Reason VARCHAR()

  );



  SELECT * FROM EmployeeLeave EL

  LEFT JOIN MST_LeaveReason LR ON LR.ReasonId = EL.LeaveType


Above query will not work as LeaveType is not always number. I want this join to work only if the LeaveType is number. How can i implement it. Please help.



Thanks in advance.






sql sql-server join







share|improve this question























  • If your varchar is only going to have a length of 1, why not use char(1) and save the overhead of having a "variable" length?

    – Larnu
    Nov 22 '18 at 11:48













  • @Larnu: VARCHAR() is (fortunately?) not legal syntax. It's probably not shorthand for VARCHAR-with-no-length-which-is-implicitly-1 in this case.

    – Jeroen Mostert
    Nov 22 '18 at 11:51
















0












0








0








I have a table EmployeeLeave



  CREATE TABLE EmployeeLeave (

  EmployeeId INT,

  LeaveType VARCHAR()

  );


LeaveType can have numbers as well as string. 



  CREATE TABLE MST_LeaveReason (

  ReasonId INT,

  Reason VARCHAR()

  );



  SELECT * FROM EmployeeLeave EL

  LEFT JOIN MST_LeaveReason LR ON LR.ReasonId = EL.LeaveType


Above query will not work as LeaveType is not always number. I want this join to work only if the LeaveType is number. How can i implement it. Please help.



Thanks in advance.






sql sql-server join







share|improve this question














I have a table EmployeeLeave



  CREATE TABLE EmployeeLeave (

  EmployeeId INT,

  LeaveType VARCHAR()

  );


LeaveType can have numbers as well as string. 



  CREATE TABLE MST_LeaveReason (

  ReasonId INT,

  Reason VARCHAR()

  );



  SELECT * FROM EmployeeLeave EL

  LEFT JOIN MST_LeaveReason LR ON LR.ReasonId = EL.LeaveType


Above query will not work as LeaveType is not always number. I want this join to work only if the LeaveType is number. How can i implement it. Please help.



Thanks in advance.






sql sql-server join




sql sql-server join






share|improve this question













share|improve this question











share|improve this question




share|improve this question










asked Nov 22 '18 at 11:46









ErmaErma

104313




104313













  • If your varchar is only going to have a length of 1, why not use char(1) and save the overhead of having a "variable" length?

    – Larnu
    Nov 22 '18 at 11:48













  • @Larnu: VARCHAR() is (fortunately?) not legal syntax. It's probably not shorthand for VARCHAR-with-no-length-which-is-implicitly-1 in this case.

    – Jeroen Mostert
    Nov 22 '18 at 11:51





















  • If your varchar is only going to have a length of 1, why not use char(1) and save the overhead of having a "variable" length?

    – Larnu
    Nov 22 '18 at 11:48













  • @Larnu: VARCHAR() is (fortunately?) not legal syntax. It's probably not shorthand for VARCHAR-with-no-length-which-is-implicitly-1 in this case.

    – Jeroen Mostert
    Nov 22 '18 at 11:51



















If your varchar is only going to have a length of 1, why not use char(1) and save the overhead of having a "variable" length?

– Larnu
Nov 22 '18 at 11:48







If your varchar is only going to have a length of 1, why not use char(1) and save the overhead of having a "variable" length?

– Larnu
Nov 22 '18 at 11:48















@Larnu: VARCHAR() is (fortunately?) not legal syntax. It's probably not shorthand for VARCHAR-with-no-length-which-is-implicitly-1 in this case.

– Jeroen Mostert
Nov 22 '18 at 11:51







@Larnu: VARCHAR() is (fortunately?) not legal syntax. It's probably not shorthand for VARCHAR-with-no-length-which-is-implicitly-1 in this case.

– Jeroen Mostert
Nov 22 '18 at 11:51














1 Answer
1






active

oldest

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3














Use try_convert():



SELECT *

FROM EmployeeLeave EL LEFT JOIN

     MST_LeaveReason LR

     ON LR.ReasonId = TRY_CONVERT(INT, EL.LeaveType);


You can also do this in the other direction:



SELECT *

FROM EmployeeLeave EL LEFT JOIN

     MST_LeaveReason LR

     ON CONVERT(VARCHAR(255), LR.ReasonId) = EL.LeaveType;


Then, work on fixing the data model. JOIN keys should be of the same type. Such conversions have a drastic affect on performance.






share|improve this answer























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    1 Answer
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    1 Answer
    1






    active

    oldest

    votes









    active

    oldest

    votes






    active

    oldest

    votes









    3














    Use try_convert():



    SELECT *
    
FROM EmployeeLeave EL LEFT JOIN
    
     MST_LeaveReason LR
    
     ON LR.ReasonId = TRY_CONVERT(INT, EL.LeaveType);


    You can also do this in the other direction:



    SELECT *
    
FROM EmployeeLeave EL LEFT JOIN
    
     MST_LeaveReason LR
    
     ON CONVERT(VARCHAR(255), LR.ReasonId) = EL.LeaveType;


    Then, work on fixing the data model. JOIN keys should be of the same type. Such conversions have a drastic affect on performance.






    share|improve this answer




























      3














      Use try_convert():



      SELECT *
      
FROM EmployeeLeave EL LEFT JOIN
      
     MST_LeaveReason LR
      
     ON LR.ReasonId = TRY_CONVERT(INT, EL.LeaveType);


      You can also do this in the other direction:



      SELECT *
      
FROM EmployeeLeave EL LEFT JOIN
      
     MST_LeaveReason LR
      
     ON CONVERT(VARCHAR(255), LR.ReasonId) = EL.LeaveType;


      Then, work on fixing the data model. JOIN keys should be of the same type. Such conversions have a drastic affect on performance.






      share|improve this answer


























        3












        3








        3







        Use try_convert():



        SELECT *
        
FROM EmployeeLeave EL LEFT JOIN
        
     MST_LeaveReason LR
        
     ON LR.ReasonId = TRY_CONVERT(INT, EL.LeaveType);


        You can also do this in the other direction:



        SELECT *
        
FROM EmployeeLeave EL LEFT JOIN
        
     MST_LeaveReason LR
        
     ON CONVERT(VARCHAR(255), LR.ReasonId) = EL.LeaveType;


        Then, work on fixing the data model. JOIN keys should be of the same type. Such conversions have a drastic affect on performance.






        share|improve this answer













        Use try_convert():



        SELECT *
        
FROM EmployeeLeave EL LEFT JOIN
        
     MST_LeaveReason LR
        
     ON LR.ReasonId = TRY_CONVERT(INT, EL.LeaveType);


        You can also do this in the other direction:



        SELECT *
        
FROM EmployeeLeave EL LEFT JOIN
        
     MST_LeaveReason LR
        
     ON CONVERT(VARCHAR(255), LR.ReasonId) = EL.LeaveType;


        Then, work on fixing the data model. JOIN keys should be of the same type. Such conversions have a drastic affect on performance.







        share|improve this answer












        share|improve this answer



        share|improve this answer










        answered Nov 22 '18 at 11:48









        Gordon LinoffGordon Linoff

        781k35310414




        781k35310414
































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