最简单理解Mysql共享、排他锁和乐观、悲观锁

版权声明：本文为博主原创文章，未经博主允许不得转载。 https://blog.csdn.net/u010739551/article/details/83142789

共享锁
select * from xx where id = 10 lock in share mode

排他锁
select * from xx where id = 10 for update

乐观锁
select num,version from xx where id = 10
update xx set num=num-1 where id =10 and xx.version = 32

悲观锁
select num from xx where id = 10 for update
update xx set num=num-1 where id = 10

乐观锁和悲观锁不是真实存在的锁，是两个使用场景，其中悲观锁用到了排它锁，乐观锁没有用锁，可能提交失败，可尝试多次重试