多列查詢結果與3個引用相同的字段

Question

可能重複：
sql query joining two columns with one

所以我有一些麻煩，在MySQL中獲得的查詢權。

這是我現在使用

DROP TABLE IF EXISTS `qualifications`; 
CREATE TABLE `qualifications`(
    `activity` int NOT NULL, 
    `group` int NOT NULL, 
`tournament` int NOT NULL, 
`judge_1` int NOT NULL, 
`grade_1` int NOT NULL, 
`judge_2` int NOT NULL, 
`grade_2` int NOT NULL, 
`judge_3` int NOT NULL, 
`grade_3` int NOT NULL, 
PRIMARY KEY(`activity`,`group`), 
FOREIGN KEY(`activity`) REFERENCES `activities`(`id`), 
FOREIGN KEY(`group`) REFERENCES `groups`(`id`), 
FOREIGN KEY(`judge_1`) REFERENCES `judges`(`id`), 
FOREIGN KEY(`judge_2`) REFERENCES `judges`(`id`), 
FOREIGN KEY(`judge_3`) REFERENCES `judges`(`id`), 
FOREIGN KEY(`tournament`) REFERENCES `tournaments`(`id`) 
)ENGINE=InnoDB, DEFAULT CHARSET=utf8; 

我要的是讓活動名稱，組名，賽事名稱表，以及所有3名法官的名字和成績。這裏的查詢我到目前爲止：

select a.name as Game, t.name as Tornament, g.name as "Group", j.name as Judge1, j.name as Judge2, (q.grade_1+q.grade_2+q.grade_3) as Grades from activities a, groups g, judges j, tournaments t, qualifications c where 
a.id = q.activity and t.id = q.tournament and g.id = q.group and g.id = 2; 

當然，這工作得很好，除了法官的名字......我怎麼能得到一個結果，3名法官？

謝謝大家，如果我不能很好地解釋我自己，對不起。

Answer 1

與Judges表一起使用以獲取名稱，假定名稱存在。

select a.name as Game, t.name as Tornament, g.name as "Group", 
      j1.name as Judge1, 
      j2.name as Judge2, 
      j3.name as Judge3, 
      (q.grade_1+q.grade_2+q.grade_3) as Grades 
    from activities a JOIN judges j1 
     ON a.judge_1 = j1.id 
     JOIN judges j2 
     ON a.judge_2 = j2.id 
     JOIN judges j3 
     ON a.judge_3 = j3.id 
     JOIN qualifications q 
     ON a.id = q.activity 
     JOIN tournaments t 
     ON t.id = q.tournament 
     JOIN groups g 
     ON g.id = q.group 
    WHERE g.id = 2; 

Answer 2

作爲替代@Yogendra Singh's answer，如果你能忍受的名字被連接成分隔的字符串（可以作爲分隔符像U+001e使用），您可以通過分組僅使judges表中的一條通結果與GROUP_CONCAT()judges.name列彙總：

SELECT a.name        AS Game, 
     t.name        AS Tournament, 
     g.name        AS Group, 
     GROUP_CONCAT(j.name SEPARATOR 0x1e) AS Judges, 
     q.grade_1 + q.grade_2 + q.grade_3 AS Grades 
FROM  activities  a 
    JOIN judges   j ON j.id IN (a.judge_1, a.judge_2, a.judge_3) 
    JOIN qualifications q ON a.id = q.activity 
    JOIN tournaments t ON t.id = q.tournament 
    JOIN groups   g ON g.id = q.group 
WHERE g.id = 2 
GROUP BY a.id, t.id