WHERE usage and examples

Overview

WHERE filters source rows before grouping and aggregation, and only rows whose predicate is TRUE continue through the query. Combine predicates with AND, OR, and NOT, using parentheses to make precedence explicit. Test NULL with IS NULL or IS NOT NULL rather than = NULL.

Basic syntax

SELECT * FROM orders WHERE amount > 1000;

Examples

WHERE example

The strict greater-than predicate returns only amounts 1200 and 1500; a row whose amount is exactly 1000 would not satisfy it.

Sample table

Table：orders

orders
id	customer_id	product_id	name	department	amount	status	created_at	discount
1	101	201	Alice	Sales	1200	paid	2026-01-03	0
2	102	202	Bob	IT	900	pending	2026-01-08	50
3	101	201	Cindy	Sales	1500	paid	2026-02-02	100
4	104	203	David	HR	700	cancelled	2026-02-15	0

Run result

result
id	customer_id	product_id	name	department	amount	status	created_at	discount
1	101	201	Alice	Sales	1200	paid	2026-01-03	0
3	101	201	Cindy	Sales	1500	paid	2026-02-02	100

Common issues

What is the difference between WHERE and HAVING?

WHERE filters raw rows before grouping, while HAVING filters aggregate results after GROUP BY.

Can WHERE contain multiple conditions?

Yes. Use AND, OR, and NOT. Add parentheses when conditions become complex.

Can WHERE check NULL values?

Yes, but use IS NULL or IS NOT NULL instead of = NULL.

Keep reading

LIKE IN BETWEEN EXISTS IS NULL AND / OR SELECT DISTINCT

WHERE