目录故事开场：面试官的“刁难”为什么子查询经常会慢？优化方法一：用关联查询替代子查询优化方法二：优化GROUP BY和DISTINCT优化方法三：关联查询中，使用标识列分组更高效优化方法四：WITH ROLLUP要慎用
Mozilla & IE developers seem to have simultaneously changed the implementation of their height elements to represent the Opera implementation... which I previously did not have to worry about.
目录1.where后面嵌套子查询2.from后面嵌套子查询*3.在select 后面嵌套子查询4.union5.*limit定义：select语句中嵌套select语句，被嵌套的select语句是子查询。
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