为什么不用 exists/table join
非用in这样低效率的东西呢?select * from table1 where field1 in (select field1 from table2);select * from a where exists (select 1 from b where b.col1 = a.col1)
非用in这样低效率的东西呢?select * from table1 where field1 in (select field1 from table2);select * from a where exists (select 1 from b where b.col1 = a.col1)
2:请认真学习一下基本sql语法