2 Marks Learning Outcome(3): Create Entity-Relationship model, Rel

2 Marks

Learning Outcome(3):
Create Entity-Relationship model, Relational model, and write SQL queries.

Question One
Based on your understanding of specialization and generalization constraints, use your own words to define and discuss the two primary constraints: Disjointness Constraint and Completeness Constraint.
Answer:
2 Marks

Learning Outcome(3):
Create Entity-Relationship model, Relational model, and write SQL queries.

Question Two Show the schema mapping of the following Payment EER schema diagram, using Option 8A: Multiple relations-Superclass and subclasses.
Answer:

2 Marks

Learning Outcome(3):
Create Entity-Relationship model, Relational model, and write SQL queries.

Question Three SQL constraints are used to specify rules for the data in a table. From what has been studied, what is the benefit of using constraints in DB. Also, explain three common SQL constraints.
2 Marks

Learning Outcome(3):
Create Entity-Relationship model, Relational model, and write SQL queries.

Question Four Using the relational algebra operations, write the following queries on the COMPANY relational database schema shown in the figure below.
Retrieve the address of employees in department 2 who work less than 5 hours per week on the ‘ProductX’ project.
Retrieve the names and salary of employees who work on every project.

Answer

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