Question

我有一个包含四个表的小型MS Access数据库，并且正在使用SELECT COUNT查询，该查询涉及所有表。任何帮助将不胜感激。

数据库概述：

TABLE       COLUMNS

Person         Person_ID |....
Games          Game_ID | Name |....
Played_Games   Played_Games_ID | Game_ID |....
Participation  Played_Games_ID | Person_ID |...

列出所有游戏以及每次游戏总共玩了多少次：

SELECT DISTINCT
Games.Name,
(SELECT COUNT(*) FROM Played_Games WHERE Played_Games.Game_ID = Games.Game_ID) AS TimesPlayed
FROM Games
ORDER BY Games.Name

这很有用，但我还要列出某一群人的每个游戏玩了多少次

我已经使用下面的代码（第4行）取得了一些进展，但我仍然遇到一个小问题：

最里面括号后面的Games.Game_ID引用不再链接到当前的Game_ID，就像在上面的代码中一样。它现在似乎未定义。当我在MS Access Query Designer中运行它进行测试时，它会要求我输入Games.Game_ID的值。如果我然后输入一些随机的Game_ID，代码就会“完美地”运行，但是正如你可能已经想到的那样，TimesPlayedByGroupMembers的值对于记录集中的每一行都是相同的，并且对于我输入的那个特定的Game_ID只有

SELECT DISTINCT
Games.Name,
(SELECT COUNT(*) FROM Played_Games WHERE Played_Games.Game_ID = Games.Game_ID) AS TimesPlayed,
(SELECT COUNT(*) FROM (SELECT DISTINCT Played_Games_ID FROM Participation WHERE Played_Games_ID IN (SELECT Played_Games_ID FROM Played_Games WHERE Game_ID = Games.Game_ID) AND Person_ID IN (26, 27, 28))) AS TimesPlayedByGroupMembers
FROM Games
ORDER BY Games.Name

我将尝试从内到外解释我的代码所做和/或应该做什么

最里面的括号列出了涉及当前游戏的Played_Games_ID，但这不起作用，因为Games.Game_ID没有链接到当前的Game_ID

中间括号（包括上面的括号）列出了涉及当前游戏和一个或多个所选人员的Played_Games_ID。这里列出的Person_ID只是一个例子，这部分代码正在运行

最外面的括号（包括上面所有）计算一个或多个选定人员每场比赛的次数

我真的坚持这一点，所以任何帮助将不胜感激

感谢您的时间

Answer 1

您的第一个查询通常更常见：

SELECT
Games.Name, COUNT(Played_Games.Game_ID) AS TimesPlayed
FROM Games
INNER JOIN Played_Games ON Played_Games.Game_ID = Games.Game_ID
GROUP BY Games.Name
ORDER BY Games.Name

这可能与您第二次查询后的情况相近：

SELECT
Games.Name, COUNT(Participation.Played_Games_ID) AS TimesPlayedByGroupMembers
FROM Games
INNER JOIN Played_Games ON Played_Games.Game_ID = Games.Game_ID
INNER JOIN Participation ON Participation.Played_Games_ID = Played_Games.Played_Games_ID
WHERE Participation.Person_ID IN (26, 27, 28)
GROUP BY Games.Name
ORDER BY Games.Name

Answer 2

我的Access语法有点生疏，我对你的表格结构并不是100％肯定，但我认为以下内容是可行的。

SELECT  Games.Name, 
        TimesPlayed,
        TimesPlayedByGroupMembers
FROM    Games
        INNER JOIN 
        (   SELECT  Game_ID, 
                    COUNT(*) AS TimesPlayed,
                    SUM(IIF(ISNULL(Participation.Played_Games_ID),0,1)) AS TimesPlayedByGroupMembers
            FROM    Played_Games 
                    LEFT JOIN 
                    (   SELECT  Played_games_ID 
                        FROM    Participation 
                        WHERE   Person_ID IN (1, 2) 
                        GROUP BY Played_games_ID 
                    ) AS Participation 
                        ON Participation.Played_Games_ID = Played_Games.Played_Games_ID
            GROUP BY Game_ID
        ) AS Played_Games
            ON Played_Games.Game_ID = Games.Game_ID
ORDER BY Games.Name

附录：

要将尚未播放的游戏显示为0，请使用以下内容：

SELECT  Games.Name, 
        IIF(ISNULL(TimesPlayed),0,TimesPlayed) AS TimesPlayed,
        IIF(ISNULL(TimesPlayedByGroupMembers),0,TimesPlayedByGroupMembers) AS TimesPlayedByGroupMembers
FROM    Games
        LEFT JOIN 
        (   SELECT  Game_ID, 
                    COUNT(*) AS TimesPlayed,
                    SUM(IIF(ISNULL(Participation.Played_Games_ID),0,1)) AS TimesPlayedByGroupMembers
            FROM    Played_Games 
                    LEFT JOIN 
                    (   SELECT  Played_games_ID 
                        FROM    Participation 
                        WHERE   Person_ID IN (1, 2) 
                        GROUP BY Played_games_ID 
                    ) AS Participation 
                        ON Participation.Played_Games_ID = Played_Games.Played_Games_ID
            GROUP BY Game_ID
        ) AS Played_Games
            ON Played_Games.Game_ID = Games.Game_ID
ORDER BY Games.Name

SQL：SELECT COUNT涉及几个表

2 个答案: