BEGIN { WORK | TRANSACTION }
This signifies that a new transaction has been started.
This indicates that a transaction was already in progress.
BEGIN begins a user transaction which PostgreSQL will guarantee is serialisable with respect to all concurrently executing transactions. PostgreSQL uses two-phase locking to perform this task. If the transaction is committed, PostgreSQL will ensure either that all updates are done orelse that none of them are done. Transactions have the standard ACID (atomic, consistent, isolatable, and durable) property.
The keyword TRANSACTION is just a cosmetic alternative to WORK. Neither keyword need be specified.
BEGIN statement is a PostgreSQL language extension.
Refer to the LOCK statement for further information about locking tables inside a transaction.
Use COMMIT or ROLLBACK to terminate a transaction.
To begin a user transaction:
BEGIN WORK;
There is no explicit "BEGIN WORK" in SQL92; transaction initiation is always implicit and it terminates either with a COMMIT or with a ROLLBACK statement.