对多表联合查询的SQl语句的改进,大幅提高查询性能 (转) 常用的多表联合查询的sql语句: select table1.ID from table1 inner join table2 on table1.ID=table2.ID where table2.col2='xxx' 改进后: select a.ID from table1 a, (select col1,ID from table2 where col2='xxx') b where a.ID=b.ID