select a.msg_id, a.com_id, a.data, a.ctime from sns_user_03.user_request_86 a where 5 (select count(*) from sns_user_03.user_request_86 where uid=8880386 and com_id = a.app_id and msg_id a.msg_id ) order by a.ctime; 上面的sql實(shí)現(xiàn)分組查詢，

select a.msg_id, a.com_id, a.data, a.ctime from sns_user_03.user_request_86 a where 5 > (select count(*) from sns_user_03.user_request_86 where uid=8880386 andcom_id= a.app_id and msg_id > a.msg_id ) order by a.ctime;

上面的sql實(shí)現(xiàn)分組查詢，每組最多顯示5條記錄，按照時(shí)間排序

select @rank:=0;

select msg_id, app_id, data, ctime, rank from ( select a.msg_id, a.app_id, a.data, a.ctime, if(@appid!=a.app_id,@rank:=@rank+1,@rank:=@rank) as rank, @appid:=a.app_id from sns_user_03.user_request_86 a where 5 > (select count(*) from sns_user_03.user_request_86 where uid=8880386 and app_id = a.app_id and msg_id > a.msg_id ) and @rank <= 4 order by a.msg_id desc ) `temp` where rank >2 and rank <=4;

上面實(shí)現(xiàn)取第3到第4組，每組5條記錄，按時(shí)間排序

這只是單純DB實(shí)現(xiàn)，在實(shí)際應(yīng)用中，對于這樣耗時(shí)的DB操作應(yīng)當(dāng)盡量避免，最好將數(shù)據(jù)cache出來，在邏輯層做這種復(fù)雜操作

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