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 A.a... 阅读全文
posted @ 2008-09-05 09:14
meil
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