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數據庫表結構:sc數據庫 sid：學生idblog cid：課程idci socre：分數it 需求：查詢每門課程分數最高的三個學生class   select a.* from sc a where 3 > (select count(*) from sc where a.cid=cid and a.socre>score)select order by a.cid,a.score desc數據

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