HAVING is an additional filter on Aggregate totals. You can control the number of rows returned with a Having clause based on aggregate totals.

Real usage

HAVING works with Aggregate functions. It is an extra WHERE condition in SQL.

Syntax for HAVING

SELECT DEPT_NO, AVG(SALARY)
FROM EMPLOYEE_TABLE
WHERE DEPT_NO IN(10,20,30)
GROUP BY (DEPT_NO)
HAVING AVG(SALARY)>45000
ORDER BY 1;

WHERE vs HAVING

1. The WHERE clause filters rows on a condition. The HAVING clause filters on Aggregate totals.
2. The WHERE clause is a generic filter.
3. HAVING clause is not generic. It is based on a certain value. Also, you can say literals.

Five top Aggregate functions

MIN – The Minimum Value.
MAX – The Maximum Value.
AVG – The Average of the Column Values.
SUM – The Sum Total of the Column Values.
COUNT – The Count of the Column Values.

Video on Having Vs Where

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