如何与多值列结合？

Question

我有两个表：

Game and Developer

“我的游戏”表具有以下列：

Release Date Origin Date DeveloperID 

并且我的Developer表具有以下列：

DevId Games 

有了数据，这些表可能看起来像这样：

Game:
Release Date Origin Date GameId
  11/20/2017  11/09/2015    G-1
  06/07/1999  03/04/1995    G-2
  08/31/2015  02/09/2010    G-3

Developer表可能类似于：

DevId Games
 D-1   G-1, G-2
 D-2   G-3
 D-3   G1, G2, G3

游戏可以具有多个值，并且它们是在下拉列表中选择的。

我想在Games值和Game表的GameId之间创建一个关系，并连接与开发人员关联的每个Game的发布日期和原始日期。

所以对于D1，我想要类似的东西

D1 Dates - 11/20/2017, 11/09/2017, 06/07/1999, 03/04/1995 since G-1 and G-2 are associated with D1 
D2 Dates - only 08/31/2015, 02/09/2010
D3 Dates - 11/20/2017, 11/09/2015, 06/07/1999, 03/04/1995, 08/31/2015, 092/09/2010 since all of the Games are associated with this Dev.

我现在所拥有的并没有削减。分组不正确，仅列出了6行作为

11/20/2017
11/09/2015
06/07/1999 
03/04/1995
08/31/2015
02/09/2010

这是我的尝试：

SELECT [Origin Date] & ',' & [Release Date] FROM Game INNER JOIN Developer ON Game.GameId = Developer.Games.Value;

任何帮助将不胜感激

Answer 1

这假定游戏数限制为3。如果不是这种情况，则可能必须编写另一个子查询来查找最大游戏数并构造等效的列数。

WITH cte AS
(
SELECT DevID, g_1, g_2, g_3
FROM
(
SELECT DevID, ROW_NUMBER() OVER() AS row_num1 FROM DevID
) a
LEFT JOIN
(
SELECT a[1] AS g_1, a[2] AS g_2, a[3] AS g_3, ROW_NUMBER() OVER() AS row_num2
FROM
(
SELECT STRING_TO_ARRAY(games, ',')
FROM DevID
) AS dt(a)
) b
ON a.row_num1 = b.row_num2
) 

SELECT DevId, ARRAY_AGG(release_date) AS release_dates, ARRAY_AGG(origin_date) AS origin_dates
FROM
(
SELECT DevID, game, Release_date, Origin_date
FROM
(
SELECT DevID, LTRIM(game) AS game
FROM
(
SELECT DevId, g_1 AS game FROM cte WHERE g_1 IS NOT NULL
UNION 
SELECT DevId, g_2 AS game FROM cte WHERE g_2 IS NOT NUll
UNION
SELECT DevId, g_3  AS game FROM cte WHERE g_3 IS NOT NULL
) a1
) al
LEFT JOIN
Game g1
ON al.game = g1.GameId
) al1 
GROUP BY DevId

输出：

DevId   ReleaseDates     OriginDates
"D-2"   "{2015-08-31}"  "{2010-02-09}"
"D-3"   "{2017-11-20,1999-06-07,2015-08-31}"    "{2015-11-09,1995-03-04,2010-02-09}"
"D-1"   "{2017-11-20,1999-06-07}"   "{2015-11-09,1995-03-04}"

Answer 2

在使用“多值”字段时，您往往不得不诉诸以下内容：

Games = GameId
OR Games LIKE GameId & ',*'
OR Games LIKE '*, ' & GameId & ',*'
OR Games LIKE '*, ' & GameId

我的MSAccess语法有点生锈，因此可能并不完全正确。

---

SELECT g.[Origin Date] & ',' & g.[Release Date] 
FROM Game AS g
INNER JOIN Developer AS d
ON d.Games = g.GameId
    OR d.Games LIKE g.GameId & ',*'
    OR d.Games LIKE '*, ' & g.GameId & ',*'
    OR d.Games LIKE '*, ' & g.GameId
;

Answer 3

不要在一个列中存储多个值！那不是数据库的工作方式。

有时候，我们真的非常，非常非常糟糕的设计被其他人所束缚。您可以这样做：

SELECT g.[Origin Date] & ',' & g.[Release Date]
FROM Game as g INNER JOIN
     Developer as d
     ON ',' & d.Games & ',' LIKE '*,' & g.GameId & ',*';

也许在MS Access中，您需要以CROSS JOIN的身份执行此操作：

  SELECT g.[Origin Date] & ',' & g.[Release Date]
FROM Game as g,
     Developer as d
WHERE ',' & d.Games & ',' LIKE '*,' & g.GameId & ',*';

Answer 4

我猜您应该执行的操作会覆盖执行以下操作的查找属性：

• 创建一个基于Developer表的查询，将两个字段都添加到查询中。
• 将字段Games重命名为Dates（输入Dates: Games作为第二个字段）
• 按如下所示更改该字段的查找属性：
  • 显示：组合框
  • RowsourceType：表/查询
  • 行来源：SELECT Game.DeveloperID, Game.[Release Date] & ", " & Game.[Origin Date] AS Expr1 FROM Game;
  • 绑定列：1
  • 列数：2
  • 列宽：0（=隐藏第一列）
  • 列表宽度：0（=自动）

尽管这并不能真正连接日期，但会像显示日期一样显示它们（多值字段显示多个值的方式）。

德语版本（用分号作为列表分隔符）的结果如下：