在事务期间锁定MYSQL表中的行 [英] Locking a row in a MYSQL table during a transaction

问题描述

我有很多这样的查询:

START TRANSACTION
SELECT amount FROM piggybank WHERE id = 2
UPDATE piggybank SET amount = amount + 5 WHERE id = 1
COMMIT

我需要确保在事务结束之前，没有其他人可以读取或写入ID为1和2的行. (锁定整个表也可以) 问题是，当我阅读MySQL手册时，它说启动一个事务将清除在启动它之前进行的所有锁定，反过来，锁定将提交任何传出的事务.

I need to make sure that no one else can read or write the rows with ID 1 and 2, until the transaction ends. (Locking the whole table would be fine too) The problem is, that when I read the MySQL manual, it said that starting a transaction will clear any locks made before starting it and in turn, locking will commit any outgoing transaction.

但是我需要同时锁定行(或表)并同时使用事务.

But I need to both lock the rows (or table) and use the transactions at the same time as well.

推荐答案

在事务内使用select ... for update查询应会为您提供所需的语义-其他更新将被锁定，而其他尝试采用相同锁定的会话将被锁定阻止直到提交:

using a select ... for update query inside the transaction should give you the semantics you want - other updates will be locked, and other sessions attempting to take this same lock will block until you commit:

START TRANSACTION
SELECT * FROM piggybank WHERE id IN (1, 2) FOR UPDATE;
SELECT amount FROM piggybank WHERE id = 2;
UPDATE piggybank SET amount = amount + 5 WHERE id = 1;
COMMIT

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