HAVING Clause in SQL

The HAVING clause is used to filter groups created by the GROUP BY clause based on a condition.

Why use HAVING?

• You use WHERE to filter rows before grouping.

• You use HAVING to filter groups after aggregation.

Syntax:

SELECT column1, AGGREGATE_FUNCTION(column2)FROM table_nameGROUP BY column1HAVING condition;

Example:

Suppose a Sales table:

Query: Regions with total sales greater than 30

SELECT Region, SUM(Amount) AS TotalSalesFROM SalesGROUP BY RegionHAVING SUM(Amount) > 30;

Result:

Key points:

• HAVING works only with grouped data.

• You can use aggregate functions (SUM(), COUNT(), etc.) in HAVING.

• You can combine WHERE and HAVING in the same query.

Example:

SELECT Region, COUNT(*) AS NumSalesFROM SalesWHERE Amount > 5GROUP BY RegionHAVING COUNT(*) > 1;

If you want, I can provide more examples or help with your specific use case!