可以的-- 不加 where select * from table_a a left join table_b b on a.id = b.id -- 加 whereselect * from table_a a left join table_b b on a.id = b.id where a.class ='one'
select *from a left join b on a.id=b.id and a.sid=b.sidwhere xxxxxx只有这样的用法