Given the relations employee (name, salary, dept-no), and department (dept-no,…
2016
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, -, ∪, ρ)
Answer: C. The sum of all employees’ salaries — Basic relational algebra operations cannot compute aggregate values such as the sum of all employees' salaries. Aggregation requires an extended relational…
- 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
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Correct answer: C
Basic relational algebra operations cannot compute aggregate values such as the sum of all employees' salaries. Aggregation requires an extended relational algebra operator.
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