A BEGIN WORK statement in SQL starts a transaction within a relational database management system (RDBMS).
Any work done after this point will not be visible to other users, until a [[COMMIT(SQL}|COMMIT]] statement is issued. A ROLLBACK statement can also be issued, which will undo any work performed since the BEGIN WORK command. Both COMMIT and ROLLBACK will end the transaction: another BEGIN WORK will need to be issued to start a new one.
Some database systems allow the synonyms BEGIN and BEGIN TRANSACTION, and may have other options available.