What does Table (NOLOCK) in Transact-SQL mean? NOLOCK is equivalent to READUNCOMMITTED. It is mean that dirty reads are allowed. No shared locks are issued to prevent other transactions from modifying data read by the current transaction, and exclusive locks set by other transactions do not block the current transaction from reading the locked data.

See SET TRANSACTION ISOLATION LEVEL READ UNCOMMITTED / READ COMMITTED / REPEATABLE READ / SNAPSHOT / SERIALIZABLE (Transact-SQL) too.

Tags: Transact-SQL