MYSQL count标量子查询怎么改left join

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.homepageidAND groundingstatus = 0) AS totalxxx,(SELECTcount(*)FROMhomepagexxxrelationWHEREhomepageid = h.homepageidAND groundingstatus = 0AND Createtime >= DATE_SUB(sysdate(), INTERVAL 7 DAY)) AS weektotalxxxFROMdesignerhomepage hWHERE1 = 1  and isrecommend=1 order by  weektotalxxx DESC,homepageid DESC;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)  AS totalscheme,ifnull(h3.cnt1,0) AS weektotalxxxFROMdesignerhomepage hLEFT JOIN (SELECTHomepageid,sum(case when  HP.Createtime >= DATE_SUB(sysdate(), INTERVAL 7 DAY) then 1 else 0 end) cnt1,count(*) cnt2FROMhomepagexxxrelation hpWHEREHP.groundingstatus = 0GROUP BYHomepageid) h3 ON h3.homepageid = h.homepageidWHERE1 = 1and isrecommend=1ORDER BYweektotalxxx DESC,homepageid DESC;

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