What is the difference between WHERE and HAVING?

The difference between WHERE and HAVING in SQL is subtle but important. Let’s break it down clearly:

Aspect	WHERE	HAVING
Purpose	Filters rows before any grouping.	Filters groups after aggregation (after GROUP BY).
Used With	Works on individual row conditions.	Works on aggregated data (like SUM(), COUNT(), AVG()).
Aggregation Functions	Cannot use aggregation functions like SUM() or COUNT() directly.	Can use aggregation functions directly.
Execution Order	Applied before GROUP BY.	Applied after GROUP BY.

Example:

Suppose we have a sales table:

id	product	amount
1	A	100
2	B	200
3	A	150
4	B	50

Using WHERE: Filter rows where amount > 100:

SELECT * FROM sales
WHERE amount > 100;

Result:

id	product	amount
2	B	200
3	A	150

Using HAVING: Find products whose total sales > 200:

SELECT product, SUM(amount) as total_sales
FROM sales
GROUP BY product
HAVING SUM(amount) > 200;

Result:

product	total_sales
A	250

✅ Key takeaway:

• WHERE → row-level filtering
• HAVING → group-level filtering