MySQL In share mode 事务锁是比较常用的共享锁

select ... from lock in share mode;   生成表级共享锁，允许其它线程读取数据但不能修改数据。

--First threadmysql> select * from test lock in share mode;+------+------+| id   | name |+------+------+|    1 | fee  |+------+------+1 row in set (0.00 sec)--Second threadmysql> update test where id = 1; ERROR 1064 (42000): You have an error in your SQL syntax; check the manual that corresponds to your MySQL server version for the right syntax to use near 'where id = 1' at line 1 mysql> update test set id = 2  where id = 1; ERROR 1205 (HY000): Lock wait timeout exceeded; try restarting transaction