not exists比not in效率要高 |
发布时间: 2012/8/4 17:02:44 |
数据库:Oracle select * from quyu_t a where a.version='256' and not exists(select 'x' from quyu_t_his b -------用not in效率低- select * from quyu_t where username not in (select username from quyu_t_his) 2个一比较简直是太明显了。 本文出自:亿恩科技【www.enkj.com】 |