BEGIN

Starts a transaction block.

BEGIN is a synonym for START TRANSACTION.

Syntax

BEGIN [ WORK | TRANSACTION ] [ isolation‑level ] [ READ [ONLY] | WRITE ]

Parameters

WORK | TRANSACTION

Optional keywords for readability only.

isolation‑level

Specifies the transaction's isolation level, which determines what data the transaction can access when other transactions are running concurrently, one of the following:

  • READ COMMITTED (default)
  • SERIALIZABLE
  • REPEATABLE READ (automatically converted to SERIALIZABLE)
  • READ UNCOMMITTED (automatically converted to READ COMMITTED)

For details, see Transactions.
READ [ONLY] | WRITE

Specifies the transaction mode, one of the following:

  • READ WRITE (default): Transaction is read/write.
  • READ ONLY: Transaction is read-only.

Setting the transaction session mode to read-only disallows the following SQL statements, but does not prevent all disk write operations:

  • INSERT, UPDATE, DELETE, and COPY if the target table is not a temporary table
  • All CREATE, ALTER, and DROP commands
  • GRANT, REVOKE, and EXPLAIN if the SQL to run is one of the statements cited above.

Privileges

None

Examples

Create a transaction with the isolation level set to READ COMMITTED and the transaction mode to READ WRITE:

=> BEGIN TRANSACTION ISOLATION LEVEL READ COMMITTED READ WRITE;
BEGIN
=> CREATE TABLE sample_table (a INT);
CREATE TABLE
=> INSERT INTO sample_table (a) VALUES (1);
OUTPUT
--------
1
(1 row)

=> END;
COMMIT

See Also