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');

Let us analyze the query step by step:

1. The outer query selects empName from the employee relation with alias E.

2. The correlated subquery inside NOT EXISTS searches for any customer assigned to employee E (C.salesRepId = E.empId) whose rating is NOT 'GOOD' (C.rating <> 'GOOD').

3. The WHERE NOT EXISTS condition evaluates to TRUE if and only if the subquery returns an empty result set, meaning there does not exist any customer of employee E with a rating other than 'GOOD'.

4. Since it is given that every employee has made a sale to at least one customer, having no customers with a rating other than 'GOOD' means that all customers of that employee have a rating of 'GOOD'.

Therefore, the query returns the names of all employees with all their customers having a 'GOOD' rating (Option D).