BEGIN

BEGIN starts a transaction on the current connection.

Synopsis

BEGIN [TRANSACTION]
      [ISOLATION LEVEL { READ COMMITTED | SNAPSHOT }]

Description

READ COMMITTED takes a new committed view for each statement. SNAPSHOT fixes the committed view when the transaction begins. Without a clause, the engine uses its configured default.

Parameters

TRANSACTION is optional noise syntax. The isolation level accepts READ COMMITTED and SNAPSHOT at execution time.

Result

Success returns an empty command result and leaves a transaction active on the connection.

Transaction behavior

A second BEGIN on the same active transaction fails. Finish the transaction with COMMIT or ROLLBACK; closing an embedded transaction handle rolls it back.

Errors and limitations

SERIALIZABLE, REPEATABLE READ and READ UNCOMMITTED parse but are explicitly rejected by the executor. The 1.2 CLI drops an isolation clause and starts its default transaction; use embedded or TCP begin_with_isolation for SNAPSHOT.

Privileges

BEGIN needs an authenticated session with CONNECT. Statements inside the transaction are authorized independently when they execute.

Example

CREATE TABLE ref_begin (id INTEGER PRIMARY KEY);
BEGIN;
INSERT INTO ref_begin VALUES (1);
ROLLBACK;
SELECT id FROM ref_begin;