WITH (NOLOCK) in SQL Server: why people put it on, and why you should not

NOLOCK means “do not wait for other people’s locks.” You can read a value that never committed. Reports go out. Then the number changes.

What you will see in old scripts

SELECT order_id, total_amount
FROM Orders WITH (NOLOCK)
WHERE order_date >= CAST(GETDATE() AS date);

Someone put it on because a report blocked a checkout, or the other way round. The fix is usually a better index or a replica, not dirty reads on finance numbers.