Identifying entity relationships in DBMS is used to identify a relationship between strong and weak entity.
Before beginning, let us take an example of Professor entity, which is our Strong Entity, with Professor_ID as a Primary Key −
The weak entity is Professor_Dependents entity:
Now, let us continue,
Weak Entity is dependent on Strong Entity and does not have a primary key. Weak Entity has a partial key. It is represented as double rectangle −
Other entities are dependent on Strong Entity and it has a key attribute i.e. a primary key and represented as a single rectangle.
It links the strong and weak entity and is represented by a double diamond sign.
Let us see with an example to link both the entities using Identifying Relationships:
Above we saw that, Dependent Name could not exist on its own but in relationship to a Professor.
Rest, the following we used in our E-R Diagram −
|Partial Key (Weak Entity)||Name|
|Primary Key (Strong Entity)||ID|