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2007年11月20日 #

"NOT IN", "JOIN...IS NULL", "NOT EXISTS" 之间的效率对比

摘要: 语句一:select count(*) from A where A.a not in (select a from B) 语句二:select count(*) from A left join B on A.a = B.a where B.a is null 语句三:select count(*) from A where not exists (select a from B where... 阅读全文

posted @ 2007-11-20 19:48 焰凌 阅读(802) 评论(3) 推荐(0) 编辑