Transactions

SQL Locks and SELECT FOR UPDATE

Coordinate concurrent access using row or table locks; syntax and isolation differ.

Availability: Common SQL with references for SQL standard, MySQL/MariaDB, PostgreSQL, SQL Server, SQLite and Oracle Database; syntax and feature support vary by engine and version.中文

Syntax

SELECT ... FOR UPDATE; -- support and clauses vary

Examples

Coordinate concurrent access using row or table locks; syntax and isolation differ.

SELECT id, balance FROM accounts WHERE id = 1 FOR UPDATE;

SQLite-oriented example; consult the relevant dialect manual.

SELECT id, balance FROM accounts WHERE id = 1 FOR UPDATE;

Parameters, options and clauses

Option / clause	Description
`BEGIN / START TRANSACTION`	Start a transaction; exact keywords vary by engine.
`COMMIT`	Make the transaction's changes permanent.
`ROLLBACK`	Undo uncommitted work or return to a savepoint.
`SAVEPOINT`	Mark an intermediate point within a transaction.
`Isolation level`	Choose concurrency behaviour where supported.

Dialect references

Safety note

Review a command and its target before running it. Commands that alter files, services, accounts, disks, permissions or databases may be difficult to reverse. Test in a safe environment and keep backups.

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