Question

In SQL, which clause is used to filter the results of an aggregate function?

• A. WHERE
• B. GROUP BY
• C. HAVING
• D. ORDER BY

Hint:

{WHERE} filters rows before grouping, while {HAVING} filters results after aggregate functions are applied.

Answer 1

The Correct Option is C

Concept: In SQL, aggregate functions such as:

• \texttt{SUM()}
• \texttt{COUNT()}
• \texttt{AVG()}
• \texttt{MAX()}
• \texttt{MIN()}

are used to perform calculations on a set of rows and return a single result. To filter results based on aggregate values, SQL uses the HAVING clause.
Step 1: Understand the WHERE clause.
The WHERE clause filters rows before grouping takes place. Example: \[ \texttt{SELECT * FROM Employees WHERE Salary>50000;} \] It cannot be used with aggregate functions directly.
Step 2: Understand the HAVING clause.
The HAVING clause is used to filter results after aggregation. Example: \[ \texttt{SELECT Department, COUNT(*)} \] \[ \texttt{FROM Employees} \] \[ \texttt{GROUP BY Department} \] \[ \texttt{HAVING COUNT(*)>5;} \] This query returns only those departments having more than 5 employees.
Step 3: Conclusion.
Since filtering conditions applied to aggregate functions are handled using the HAVING clause, the correct answer is: \[ \text{HAVING} \]