Consider the relation Emp-Dept with SSn as key. Ename | SSn (key) | EAddr | Dept. No. | Dept. Name | Dept. Manager | SSn
Consider the relation Emp-Dept with SSn as key.
Ename | SSn (key) | EAddr | Dept. No. | Dept. Name | Dept. Manager | SSn
Which of the following is (are) invalid operations (s)?
(i) Inserting an employee without name and address.
(ii) Inserting an employee with only SSn.
(iii) Inserting a department with no employee.
(iv) Inserting an employee without SSn.
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Correct answer: (B) (iv)
Explanation
SSn is the primary key, and by entity integrity a key cannot be null. So inserting an employee without an SSn is invalid. Name and address may be null.