MySQL三表联合查询操作举例

select max(s.`Score`) as MaxScore from score s group by s.`SubjectId`

select b.* from (
   select max(s.`Score`) as MaxScore,s.`SubjectId` as SubId from score s group by s.`SubjectId`)
   f,score b where b.`SubjectId` = f.SubId and b.`Score` = f.MaxScore

SELECT b.`StudentId`,f.SubName,b.`Score` FROM (
   SELECT MAX(s.`Score`) AS MaxScore,s.`SubjectId` AS SubId,sub.`Name` AS SubName
   FROM score s LEFT JOIN SUBJECT AS sub ON s.`SubjectId` = sub.`SubjectNo` 
   GROUP BY s.`SubjectId`)f,score b WHERE b.`SubjectId` = f.SubId AND b.`Score` = f.MaxScore

SELECT stu.Name,t.* FROM 
    (SELECT b.`StudentId` AS Sid,f.SubName AS SubName,b.`Score` AS Score FROM 
         (SELECT MAX(s.`Score`) AS MaxScore,sub.`SubjectNo` AS SubNo,sub.`Name` AS SubName 
          FROM score s LEFT JOIN SUBJECT AS sub ON s.`SubjectId` = sub.`SubjectNo` GROUP BY sub.`SubjectNo`) 
    f,score b WHERE b.`StudentId` = f.SubNo AND b.`Score` = f.MaxScore) 
t LEFT JOIN student stu ON stu.StudentNo = t.Sid ORDER BY t.Score

SELECT s.`StudentId` AS Sid,
MAX(s.`Score`) AS MaxScore,sub.`Name` AS SubName FROM score s LEFT JOIN SUBJECT AS sub ON s.`SubjectId` = 
sub.`SubjectNo` GROUP BY s.`SubjectId`

SELECT
csb_accessories_bjgh.*,
csb_accessories_bjqd.aname,
csb_accessories_bjqd.atypes,
csb_asset_directory.assetname,
csb_asset_directory.assettypes
FROM
(( csb_accessories_bjgh LEFT JOIN csb_accessories_bjqd ON csb_accessories_bjgh.accessoriesid = csb_accessories_bjqd.accessoriesid ) LEFT JOIN csb_asset_directory ON csb_accessories_bjgh.assetid = csb_asset_directory.assetid )
WHERE
csb_accessories_bjgh.id IS NOT NULL