For each strong entity type E in the ER schema create a corresponding relation R and include:
EMPLOYEE (Bdate, Address, Salary, Sex)
Simple attributes of EMPLOYEE entity type are:
Bdate, Address, Salary, Sex
Simple component attributes of a composite attribute Name of EMPLOYEE entity type are: Fname, Minit, Lname
EMPLOYEE (Bdate, Address, Salary, Sex, Fname, Minit, Lname)
The key attribute of EMPLOYEE is Ssn
EMPLOYEE (Bdate, Sex, Salary, Address, Fname, Minit, Lname, Ssn)
For each weak entity type W in the ER schema with owner entity type E, create a relation R and include:
2.1) Include all the simple attributes (or simple components of composite attributes)
of W as attributes of R.
DEPENDENT(Sex, Bdate, Relationship)
For each weak entity type W in the ER schema with owner entity type E, create a relation R and include:
2.2) Include as foreign key attributes of R, the primary key attribute(s) of the relation(s) that correspond to the owner entity type(s) E. Also include the attributes of partial key of W. These are the attributes of the primary key of W.
DEPENDENT(Sex, Bdate, Relationship, Essn, Dependent_name)
T
S
R
1
1
Case 1: One of the entity types, say T, has total participation and the second entity type has partial participation: Then Include as a foreign key in T the primary key of S. Include in S all the simple attributes of R.
Case 2: Both entity types have partial participations: Then arbitrary select one of the entity types, say T, and include its primary key in the relation corresponding to the second entity type (S) as a foreign key. Also, include in the S all the simple attributes of the 1:1 relation (K).
Case 3: Both entity types have total participations: Then merge two entity types in a single relation
Step 3: Mapping of
Binary 1:1 Relationships
K
Start_date
T
S
R
1
N
Identify the relation that represents the participating entity type at the N-side of the relationship type (T)
Include as foreign key in T the primary key of the relation S
Include any simple attributes (K) (or simple components of composite attributes) of the 1:N relationship type as attributes of T
K
WORKS_ON (Pno, Hours, Essn)
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