1. DML LOCK
2. DDL LOCK
3. INTERNAL
锁 sql 允许的锁
0 select * from tab; RS RX S SRX X
1 row share (RS) select * from tab for insert RS RX S SRX
lock tab xx in row share mode; 禁止 X ,同时禁止 默认的RX，update tab
2 row exclusive (RX) insert into tab ; RS RX
lock tab xx in row exclusive mode; 禁止 X S SRX 如果又默认RX ，一样禁止上RS 锁
3 share ( S) lock tab xx in share mode; RS S
禁止 其他用户 insert ,仅可查询
4 share row exclusive (SRX) lock tab xx in share row exclusive mode RS
禁止 X S SRX RX
5 exclusive ( X ) lock tab xx in exclusive mode 无
最强限制，不允许insert和锁定tab,仅查询
原文：https://www.cnblogs.com/jgmor/p/11386831.html