T-SQL reference › IN

IN and NOT IN in SQL Server

IN is “equals any of these.” Fine for a short list you wrote. NOT IN plus a subquery that can return NULL is a well-known trap.

A list you wrote

SELECT order_id, status, total_amount
FROM Orders
WHERE status IN ('Shipped', 'Processing')
ORDER BY order_id;

NOT IN (SELECT phone …)

If one phone is NULL, the whole NOT IN becomes unknown, and you get no rows. Use NOT EXISTS or WHERE phone NOT IN (…) AND phone IS NOT NULL. Prefer NOT EXISTS.

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