MySQL查詢以查找列中的不同值並獲取總和

Question

我的電影DVD很少，想在MySQL中創建一個簡單的數據庫。 PF數據庫結構。 正在使用一個MySQL查詢，但實際上並未列出確切的編號。 我正在看電影。 下面的查詢是-

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;

數據庫結構-

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

它顯示13個結果，而不是DB中的18個電影。 我搜索了您的問題列表，但沒有找到合適的答案。 您能否傳達我要去哪里哪里還是有更好的方法來安排此查詢？

Answer 1

更新-

您使用UNION出錯了。 它刪除重復項。 您的內部查詢返回（5,5,4,2,1,1,0），但在刪除重復項后，並集將它們轉換為（5,4,2,1,0）。

您需要使用UNION ALL來計算所有內容。 只需將所有UNION替換為UNION ALL

當您這樣做時，您會注意到，如果列之間有電影，即如果電影300在不同用戶的Movie4和Movie5列中，則它將計數兩次。

如果只需要跨所有列獲取不同的電影，則首先從各個列中獲取不同的電影，然后將它們UNION以刪除重復的電影，然后對電影計數。

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;