在4.0.18中如何在A表中删除在B表中不存在映射的数据？

例如，语句可表达为
delete from clients where not exists(select * from branches where branches.cid = clients.cid);但4.0.18不支持子查询
在不考虑升级数据库的情况下
请问有什么其他语句可实现同样同能？

--1.
delete from clients where cid not in(select cid from branches); --2.
delete clients
from clients,branches
where clients.cid<>branches.cid;
--1.
delete from clients where cid not in(select cid from branches); 这句还是用到了子查询
delete clients.* FROM clients LEFT JOIN branches USING (cid) WHERE branches.cid IS NULL后来用了这句，问题解决。