Question

通过优化计算项目的子查询来实现斗争：

SELECT @crewid:=crewid AS `crewid`, COUNT(id) AS `number_documents`,
        (SELECT COUNT(id) FROM tblScan WHERE classification IS NOT NULL AND crewId = @crewid) AS `classified`,
        (SELECT COUNT(id) FROM tblScan WHERE classification IS NULL AND crewId = @crewid) AS `unclassified`,
        (SELECT CONCAT(name, ' ', surname) FROM tblcrew WHERE crewId = @crewid) AS `crewname`,
        (SELECT uploadeddate FROM tblScan WHERE crewid = @crewid ORDER BY uploadeddate DESC LIMIT 0,1) AS `uploadeddate`,
        (SELECT uploadedby FROM tblScan WHERE crewid = @crewid ORDER BY uploadedby DESC LIMIT 0,1) AS `uploadedby`,
        (SELECT updateddate FROM tblScan WHERE crewid = @crewid AND updateddate IS NOT NULL ORDER BY updateddate DESC LIMIT 0,1) AS `updateddate`,
        (SELECT updatedby FROM tblScan WHERE crewid = @crewid AND updatedby IS NOT NULL ORDER BY updatedby DESC LIMIT 0,1) AS `updatedby`
        FROM tblScan

希望有人可以提供帮助

谢谢，德尔斯

Answer 1

SELECT 
   `tblScan`.`crewId` AS `crewid`
   COUNT(`tblScan`.`id`) AS `number_documents`,
   SUM(IF(`tblScan`.`classification` IS NOT NULL,1,0)) AS `classified`,
   SUM(IF(`tblScan`.`classification` IS NULL,1,0)) AS `unclassified`,
   CONCAT(`tblcrew`.`name`, ' ', `tblcrew`.`surname`) AS `crewname`,
   MAX(`tblScan`.`uploadeddate`) AS `uploadeddate`,
   MAX(`tblScan`.`uploadedby`) AS `uploadedby`,
   MAX(IFNULL(`tblScan`.`updateddate`,'0000-01-01')) AS `updateddate`,
   MAX(IFNULL(`tblScan`.`updatedby`,'0')) AS `updatedby`
FROM tblScan
INNER JOIN tblcrew ON `tblcrew`.`crewId`=`tblScan`.`crewId`
GROUP BY `tblScan`.`crewId`

MySQL，优化子查询

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