Question

我的电影DVD很少，想在MySQL中创建一个简单的数据库。 PF DB结构。我有一个MySQL查询实际上没有列出确切的否。我正在拍的电影。以下查询是 -

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

它显示了13个结果，而不是数据库中的18个电影。我搜索了你的问题清单，但没有找到合适的答案。你能告诉我哪里出错了，还是有更好的方法来安排这个问题？

Answer 1

更新 -

UNION你出错了。它删除重复。你的内部查询正在返回（5,5,4,2,1,1,0），但是在删除重复项后，联合将它们转换为（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

即可

当你这样做时，你会注意到如果跨列有电影，即如果电影300在列Movie4和Movie5不同的用户，它将计数两次。

如果您需要在所有列中获取不同的电影，请先从各个列中获取不同的电影，UNION删除重复项，然后计算电影。

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;

MySQL Query用于在列中查找不同的值并获取总和

1 个答案: