关于表中列行的问题

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?这是在坛子里一名网友发布的面试题 使用SQL语句把表一转为表二 我总结了下几位回帖人的答案 并做了测试 把比较好的贴上来 ?

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select p_id,sum(case when s_id=1 then p_num else 0 end) as s1_id,sum(case when s_id=2 then p_num else 0 end) as s2_id,sum(case when s_id=3 then p_num else 0 end) as s3_idfrom mypro c group by p_id
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