Given the relations
employee (name, salary, dept-no), and
department (dept-no, dept-name,address)

Which of the following queries cannot be expressed using the basic
relational algebra operations (σ, π, 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: The sum of all employees’ salaries can not be found using these above operations as to calculate sum we need aggregate functions and operators.
So, option (C) is correct.

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