Given the relations
employee (name, salary, deptno) and
department (deptno, deptname, address)
Which of the following queries cannot be expressed using the basic relational algebra operations (U, -, x, 
, 
, p)?
(A) Department address of every employee
(B) Employees whose name is the same as their department name
(C) The sum of all employees’ salaries
(D) All employees of a given department
Answer: (C)
Explanation: See question 1 of https://www.geeksforgeeks.org/database-management-system-set-1/
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