START TRANSACTION

Description

START TRANSACTION starts a transaction. If the isolation level or read/write mode is specified, a new transaction will have those characteristics. You can also specify them using SET TRANSACTION.

Syntax

Format 1: START TRANSACTION

START TRANSACTION
  [ 
    { 
       ISOLATION LEVEL { READ COMMITTED | SERIALIZABLE | REPEATABLE READ }
       | { READ WRITE | READ ONLY }
     } [, ...] 
  ];

Format 2: BEGIN

BEGIN [ WORK | TRANSACTION ]
  [ 
    { 
       ISOLATION LEVEL { READ COMMITTED | SERIALIZABLE | REPEATABLE READ }
       | { READ WRITE | READ ONLY }
      } [, ...] 
  ];

Parameters

WORK | TRANSACTION
Specifies the optional keyword in BEGIN format without functions.
ISOLATION LEVEL
Specifies the transaction isolation level that determines the data that a transaction can view if other concurrent transactions exist.

The isolation level cannot be changed after data is modified using SELECT, INSERT, DELETE, UPDATE, FETCH, or COPY in the transaction.

Value range:
- READ COMMITTED: Only committed data can be read. It is the default value.
- REPEATABLE READ: Only the data committed before transaction start is read. Uncommitted data or data committed in other concurrent transactions cannot be read.
- SERIALIZABLE: Currently, this isolation level is not supported in GaussDB. It is equivalent to REPEATABLE READ.
READ WRITE | READ ONLY
Specifies the transaction access mode (read/write or read only).

Examples

-- Start a transaction in default mode.
openGauss=# START TRANSACTION;
openGauss=# SELECT * FROM tpcds.reason;
openGauss=# END;

-- Start a transaction in default mode.
openGauss=# BEGIN;
openGauss=# SELECT * FROM tpcds.reason;
openGauss=# END;

-- Start a transaction with the isolation level being READ COMMITTED and the access mode being READ WRITE:
openGauss=# START TRANSACTION ISOLATION LEVEL READ COMMITTED READ WRITE;
openGauss=# SELECT * FROM tpcds.reason;
openGauss=# COMMIT;