MySQL中的行级锁SELECT FOR UPDATE 和LOCK IN SHARE MODE 区别

SELECT ... LOCK IN SHARE MODE sets a shared mode lock on the rows read. A shared mode lock enables other sessions to read the rows but not to modify them. The rows read
are the latest available, so if they belong to another transaction that has not yet committed, the read blocks until that transaction ends.

在读取的行上设置一个共享模式的锁。这个共享锁允许其它session读取数据但不允许修改它。 行读取的是最新的数据，如果他被其它事务使用中而没有提交，读取锁将被阻塞知道那个事务结束。

SELECT ... FOR UPDATE sets an exclusive lock on the rows read. An exclusive lock prevents other sessions from accessing the rows for reading or writing.

在读取行上设置一个排他锁。阻止其他session读取或者写入行数据