GATE | GATE-CS-2014-(Set-3) | Question 65

Consider the following relational schema:

  employee(empId, empName, empDept)
  customer(custId, custName, salesRepId, rating)

salesRepId is a foreign key referring to empId of the employee relation. Assume that each employee makes a sale to at least one customer. What does the following query return?

SELECT empName
       FROM employee E
       WHERE NOT EXISTS ( SELECT custId
                          FROM customer C
                          WHERE C.salesRepId = E.empId
                            AND C.rating <> `GOOD`);

(A)

Names of all the employees with at least one of their customers having a ‘GOOD’ rating.

(B)

Names of all the employees with at most one of their customers having a ‘GOOD’ rating.

(C)

Names of all the employees with none of their customers having a ‘GOOD’ rating.

(D)

Names of all the employees with all their customers having a ‘GOOD’ rating.

Answer

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