Wednesday, 12 September 2018

Exercise 3.8 Answer each of the following


Exercise 3.8 Answer each of the following


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Exercise 3.8 Answer each of the following questions briefly. The questions are based on the following relational schema:

Emp(eid: integer, ename: string, age: integer, salary: real) Works(eid: integer, did: integer, pcttime: integer)
Dept(did: integer, dname: string, budget: real, managerid: integer)

1.    Give an example of a foreign key constraint that involves the Dept relation. What are the options for enforcing this constraint when a user attempts to delete a Dept tuple?

2.    Write the SQL statements required to create the above relations, including appro- priate versions of all primary and foreign key integrity constraints.
3.    Define the Dept relation in SQL so that every department is guaranteed to have a manager.
4.    Write an SQL statement to add ‘John Doe’ as an employee with eid = 101,
age = 32 and salary = 15, 000.
5.    Write an SQL statement to give every employee a 10% raise.
6.    Write an SQL statement to delete the ‘Toy’ department. Given the referential integrity constraints you chose for this schema, explain what happens when this statement is executed.


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