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:

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:

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