MySQL查询以查找列中的不同值并获取总和

Question

我的电影DVD很少，想在MySQL中创建一个简单的数据库。 PF数据库结构。 正在使用一个MySQL查询，但实际上并未列出确切的编号。 我正在看电影。 下面的查询是-

SELECT SUM(Total) as total
FROM (
SELECT COUNT(DISTINCT(Movie1)) AS Total FROM tbl_movie 
      WHERE Movie1 !='' AND Movie1 IS NOT NULL AND DVDCategory='Movie'
UNION
SELECT COUNT(DISTINCT(Movie2)) FROM tbl_movie 
       WHERE Movie2 !='' AND Movie2 IS NOT NULL AND DVDCategory='Movie'
UNION
SELECT COUNT(DISTINCT(Movie3)) FROM tbl_movie 
       WHERE Movie3 !='' AND Movie3 IS NOT NULL AND DVDCategory='Movie'
UNION
SELECT COUNT(DISTINCT(Movie4)) FROM tbl_movie 
       WHERE Movie4 !='' AND Movie4 IS NOT NULL AND DVDCategory='Movie'
UNION
SELECT COUNT(DISTINCT(Movie5)) FROM tbl_movie 
       WHERE Movie5 !='' AND Movie5 IS NOT NULL AND DVDCategory='Movie'
UNION
SELECT COUNT(DISTINCT(Movie6)) FROM tbl_movie 
       WHERE Movie6 !='' AND Movie6 IS NOT NULL AND DVDCategory='Movie'
UNION
SELECT COUNT(DISTINCT(Movie7)) FROM tbl_movie 
       WHERE Movie7 !='' AND Movie7 IS NOT NULL AND DVDCategory='Movie'
) AS Total;

数据库结构-

ID DVD Movie1   Movie2   Movie3      Movie4          Movie5   Movie6   Movie7
__________________________________________________________________
1  1  IronMan  Movie11   MindHunters  300            Jumper   7        
2  2  IronMan2 Movie22   Grey         Blood Diamond
3  3  Movie33  Red Eye   Departed     300            
4  4  Movie44  Gladiator King Kong
5  5  Movie55  Hitman

它显示13个结果，而不是DB中的18个电影。 我搜索了您的问题列表，但没有找到合适的答案。 您能否传达我要去哪里哪里还是有更好的方法来安排此查询？

Answer 1

更新-

您使用UNION出错了。 它删除重复项。 您的内部查询返回（5,5,4,2,1,1,0），但在删除重复项后，并集将它们转换为（5,4,2,1,0）。

您需要使用UNION ALL来计算所有内容。 只需将所有UNION替换为UNION ALL

当您这样做时，您会注意到，如果列之间有电影，即如果电影300在不同用户的Movie4和Movie5列中，则它将计数两次。

如果只需要跨所有列获取不同的电影，则首先从各个列中获取不同的电影，然后将它们UNION以删除重复的电影，然后对电影计数。

SELECT COUNT(movie) as total
FROM (
SELECT DISTINCT Movie1 AS movie FROM tbl_movie 
    WHERE Movie1 !='' AND Movie1 IS NOT NULL AND DVDCategory='Movie'
UNION
SELECT DISTINCT Movie2 FROM tbl_movie 
    WHERE Movie2 !='' AND Movie2 IS NOT NULL AND DVDCategory='Movie'
UNION
SELECT DISTINCT Movie3 FROM tbl_movie 
     WHERE Movie3 !='' AND Movie3 IS NOT NULL AND DVDCategory='Movie'
UNION
SELECT DISTINCT Movie4 FROM tbl_movie 
     WHERE Movie4 !='' AND Movie4 IS NOT NULL AND DVDCategory='Movie'
UNION
SELECT DISTINCT Movie5 FROM tbl_movie 
     WHERE Movie5 !='' AND Movie5 IS NOT NULL AND DVDCategory='Movie'
UNION
SELECT DISTINCT Movie6 FROM tbl_movie 
     WHERE Movie6 !='' AND Movie6 IS NOT NULL AND DVDCategory='Movie'
UNION
SELECT DISTINCT Movie7 FROM tbl_movie 
     WHERE Movie7 !='' AND Movie7 IS NOT NULL AND DVDCategory='Movie'
) AS AllDistinctMovies;