MYSQL count标量子查询怎么改left join，相信很多没有经验的人对此束手无策，为此本文总结了问题出现的原因和解决方法，通过这篇文章希望你能解决这个问题。

SELECThomepageId,userId,homepagesummary,totalviews,totalleadpercents,totalappointments,homepagestatus,linkphone,imagepath,createtime,updatetime,recommendtime,sortcode,designerimagepath,isrecommend,(SELECTcount(*)FROMhomepagexxxrelationWHEREhomepageid=h.homepageidANDgroundingstatus=0)AStotalxxx,(SELECTcount(*)FROMhomepagexxxrelationWHEREhomepageid=h.homepageidANDgroundingstatus=0ANDCreatetime>=DATE_SUB(sysdate(),INTERVAL7DAY))ASweektotalxxxFROMdesignerhomepagehWHERE1=1andisrecommend=1orderbyweektotalxxxDESC,homepageidDESC;优化后:SELECTh.homepageId,h.userId,h.homepagesummary,h.totalviews,h.totalleadpercents,h.totalappointments,h.homepagestatus,h.linkphone,h.imagepath,h.createtime,h.updatetime,h.recommendtime,h.sortcode,h.designerimagepath,h.isrecommend,ifnull(h3.cnt2,0)AStotalscheme,ifnull(h3.cnt1,0)ASweektotalxxxFROMdesignerhomepagehLEFTJOIN(SELECTHomepageid,sum(casewhenHP.Createtime>=DATE_SUB(sysdate(),INTERVAL7DAY)then1else0end)cnt1,count(*)cnt2FROMhomepagexxxrelationhpWHEREHP.groundingstatus=0GROUPBYHomepageid)h3ONh3.homepageid=h.homepageidWHERE1=1andisrecommend=1ORDERBYweektotalxxxDESC,homepageidDESC;

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