摘要：
When we use in and not in, it will take a long time to get the results. because it scans all the records of the table. we can use left join instead of in or not in like the following:1. select * from table1 where tabel1.name not in (select name from table2)is equals toselect a.* from table1 aleft jo 阅读全文
posted @ 2012-05-20 09:56 oceanlzhang 阅读(184) 评论(0) 推荐(0) 编辑