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覆巢之下焉有完卵。出来道上混,迟早是要还的。

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对多表联合查询的SQl语句的改进，大幅提高查询性能

2008-03-20 09:58:44| 分类：默认分类 | 标签： |举报 |字号大中小订阅

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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

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