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SET TRANSACTION

The SET TRANSACTION statement can be used to change the current isolation level on a GLOBAL or SESSION basis. This syntax is an alternative to SET transaction_isolation='new-value' and is included for compatibility with both MySQL, and the SQL standards.

Synopsis

SetStmt:

SetStmt

TransactionChar:

TransactionChar

IsolationLevel:

IsolationLevel

Examples

mysql> SHOW SESSION VARIABLES like 'transaction_isolation'; +-----------------------+-----------------+ | Variable_name | Value | +-----------------------+-----------------+ | transaction_isolation | REPEATABLE-READ | +-----------------------+-----------------+ 1 row in set (0.00 sec) mysql> SET SESSION TRANSACTION ISOLATION LEVEL READ COMMITTED; Query OK, 0 rows affected (0.00 sec) mysql> SHOW SESSION VARIABLES like 'transaction_isolation'; +-----------------------+----------------+ | Variable_name | Value | +-----------------------+----------------+ | transaction_isolation | READ-COMMITTED | +-----------------------+----------------+ 1 row in set (0.01 sec) mysql> SET SESSION transaction_isolation = 'REPEATABLE-READ'; Query OK, 0 rows affected (0.00 sec) mysql> SHOW SESSION VARIABLES like 'transaction_isolation'; +-----------------------+-----------------+ | Variable_name | Value | +-----------------------+-----------------+ | transaction_isolation | REPEATABLE-READ | +-----------------------+-----------------+ 1 row in set (0.00 sec)

MySQL compatibility

  • TiDB supports the ability to set a transaction as read-only in syntax only.
  • The isolation levels READ-UNCOMMITTED and SERIALIZABLE are not supported.
  • The isolation level REPEATABLE-READ is technically Snapshot Isolation. The name REPEATABLE-READ is used for compatibility with MySQL.

See also

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