Mixing
Can a weak entity be involved in both identifying and non-identifying relationships with other tables?
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Obviously a weak entity must be involved (as the child) in one or more identifying relationships, otherwise it would not be weak.
But can it, at the same time, also be the child in a non-identifying relationship?
database weak-entity identifying-relationship
edited Jan 3 at 5:24
Bhargav Rao♦
31k2092114
asked Mar 24 '17 at 1:49
S. JacksonS. Jackson
61
add a comment |
Obviously a weak entity must be involved (as the child) in one or more identifying relationships, otherwise it would not be weak.
But can it, at the same time, also be the child in a non-identifying relationship?
database weak-entity identifying-relationship
edited Jan 3 at 5:24
Bhargav Rao♦
31k2092114
asked Mar 24 '17 at 1:49
S. JacksonS. Jackson
61
add a comment |
Obviously a weak entity must be involved (as the child) in one or more identifying relationships, otherwise it would not be weak.
But can it, at the same time, also be the child in a non-identifying relationship?
database weak-entity identifying-relationship
edited Jan 3 at 5:24
Bhargav Rao♦
31k2092114
asked Mar 24 '17 at 1:49
S. JacksonS. Jackson
61
Obviously a weak entity must be involved (as the child) in one or more identifying relationships, otherwise it would not be weak.
But can it, at the same time, also be the child in a non-identifying relationship?
database weak-entity identifying-relationship
database weak-entity identifying-relationship
edited Jan 3 at 5:24
Bhargav Rao♦
31k2092114
asked Mar 24 '17 at 1:49
S. JacksonS. Jackson
61
edited Jan 3 at 5:24
Bhargav Rao♦
31k2092114
asked Mar 24 '17 at 1:49
S. JacksonS. Jackson
61
edited Jan 3 at 5:24
Bhargav Rao♦
31k2092114
edited Jan 3 at 5:24
Bhargav Rao♦
31k2092114
edited Jan 3 at 5:24
Bhargav Rao♦
31k2092114
31k2092114
asked Mar 24 '17 at 1:49
S. JacksonS. Jackson
61
asked Mar 24 '17 at 1:49
S. JacksonS. Jackson
61
asked Mar 24 '17 at 1:49
S. JacksonS. Jackson
61
61
add a comment |
add a comment |
1 Answer
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Yes, weak entity sets can participate in non-identifying relationships with other entities. By "child", I suppose you mean relationships in which the weak entity set is on the determining (many) side of the relationship. There is no restriction on the kinds of relationships in which weak entity sets may participate.
However, watch out for multiple identifying relationships. While a weak entity set can easily be the descendant of a chain of identifying relationships, multiple independent identifying relationships on the same weak entity set are unusual, and challenges the very notion of an entity set. See my answer to this question.
Note that your question title mentions relationships between tables, which confuses conceptual (ER) and physical (tabular) models. Entity relations are represented by tables, but so are relationship relations in general (only one-to-one and one-to-many relationships can be denormalized into the entity relation of a/the determining entity set, many-to-many and ternary and higher relationships still require their own tables).
edited May 23 '17 at 12:00
Community♦
11
answered Mar 24 '17 at 5:53
reaanbreaanb
7,84821530
add a comment |
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1 Answer
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1 Answer
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Yes, weak entity sets can participate in non-identifying relationships with other entities. By "child", I suppose you mean relationships in which the weak entity set is on the determining (many) side of the relationship. There is no restriction on the kinds of relationships in which weak entity sets may participate.
However, watch out for multiple identifying relationships. While a weak entity set can easily be the descendant of a chain of identifying relationships, multiple independent identifying relationships on the same weak entity set are unusual, and challenges the very notion of an entity set. See my answer to this question.
Note that your question title mentions relationships between tables, which confuses conceptual (ER) and physical (tabular) models. Entity relations are represented by tables, but so are relationship relations in general (only one-to-one and one-to-many relationships can be denormalized into the entity relation of a/the determining entity set, many-to-many and ternary and higher relationships still require their own tables).
edited May 23 '17 at 12:00
Community♦
11
answered Mar 24 '17 at 5:53
reaanbreaanb
7,84821530
add a comment |
Yes, weak entity sets can participate in non-identifying relationships with other entities. By "child", I suppose you mean relationships in which the weak entity set is on the determining (many) side of the relationship. There is no restriction on the kinds of relationships in which weak entity sets may participate.
However, watch out for multiple identifying relationships. While a weak entity set can easily be the descendant of a chain of identifying relationships, multiple independent identifying relationships on the same weak entity set are unusual, and challenges the very notion of an entity set. See my answer to this question.
Note that your question title mentions relationships between tables, which confuses conceptual (ER) and physical (tabular) models. Entity relations are represented by tables, but so are relationship relations in general (only one-to-one and one-to-many relationships can be denormalized into the entity relation of a/the determining entity set, many-to-many and ternary and higher relationships still require their own tables).
edited May 23 '17 at 12:00
Community♦
11
answered Mar 24 '17 at 5:53
reaanbreaanb
7,84821530
add a comment |
Yes, weak entity sets can participate in non-identifying relationships with other entities. By "child", I suppose you mean relationships in which the weak entity set is on the determining (many) side of the relationship. There is no restriction on the kinds of relationships in which weak entity sets may participate.
However, watch out for multiple identifying relationships. While a weak entity set can easily be the descendant of a chain of identifying relationships, multiple independent identifying relationships on the same weak entity set are unusual, and challenges the very notion of an entity set. See my answer to this question.
Note that your question title mentions relationships between tables, which confuses conceptual (ER) and physical (tabular) models. Entity relations are represented by tables, but so are relationship relations in general (only one-to-one and one-to-many relationships can be denormalized into the entity relation of a/the determining entity set, many-to-many and ternary and higher relationships still require their own tables).
edited May 23 '17 at 12:00
Community♦
11
answered Mar 24 '17 at 5:53
reaanbreaanb
7,84821530
Yes, weak entity sets can participate in non-identifying relationships with other entities. By "child", I suppose you mean relationships in which the weak entity set is on the determining (many) side of the relationship. There is no restriction on the kinds of relationships in which weak entity sets may participate.
However, watch out for multiple identifying relationships. While a weak entity set can easily be the descendant of a chain of identifying relationships, multiple independent identifying relationships on the same weak entity set are unusual, and challenges the very notion of an entity set. See my answer to this question.
Note that your question title mentions relationships between tables, which confuses conceptual (ER) and physical (tabular) models. Entity relations are represented by tables, but so are relationship relations in general (only one-to-one and one-to-many relationships can be denormalized into the entity relation of a/the determining entity set, many-to-many and ternary and higher relationships still require their own tables).
edited May 23 '17 at 12:00
Community♦
11
answered Mar 24 '17 at 5:53
reaanbreaanb
7,84821530
edited May 23 '17 at 12:00
Community♦
11
edited May 23 '17 at 12:00
Community♦
11
edited May 23 '17 at 12:00
Community♦
11
11
answered Mar 24 '17 at 5:53
reaanbreaanb
7,84821530
answered Mar 24 '17 at 5:53
reaanbreaanb
7,84821530
answered Mar 24 '17 at 5:53
reaanbreaanb
7,84821530
7,84821530
add a comment |
add a comment |
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