SQL Server可选连接

Question

我有几张桌子(确切地说,7张)我互相交叉的桌子.这部分给我一些问题;

表"行动"

 -----------------------------------------
| ID | Package ID | Action Type | Message |
 -----------------------------------------
| 40 | 100340     | 0           | OK      |
| 41 | 100340     | 12          | Error   |
| 42 | 100340     | 2           | OK      |

| 43 | 100341     | 4           | OK      |
| 44 | 100341     | 0           | Error   |
| 45 | 100341     | 12          | OK      |
 -----------------------------------------

表"包"

 ----------------------
| ID     | Name        |
 ----------------------
| 100340 | Testpackage |
| 100341 | Package xy  |
 ----------------------

我完成了交叉连接,但是当没有Package指定ID时Actions,该包上的所有操作都完全丢失,而不仅仅是Name留空 - 这正是我想要的.

因此,如果缺少引用,只需将相应的连接列留空或作为空字符串......:

 ----------------------------------------------------------------------
| Package ID | Name        | Action 0 | Action 2 | Action 4 | Action 12 |
 ----------------------------------------------------------------------
| 100340     | Testpackage | OK       | OK       |          | Error     |
| 100341     | Package xy  | Error    |          | OK       | OK        |
 ----------------------------------------------------------------------

怎么可能？

编辑

对不起,我刚看到我的示例是完全错误的,我更新了它最终应该是什么样子.

我当前的查询看起来像这样(如上所述,只是一个提取,因为实际的查询是大约三倍,包括更多的表)

SELECT
 PackageTable.ID AS PackageID,
 PackageTable.Name,
 Action0Table.Message  AS Action0,
 Action2Table.Message  AS Action2,
 Action4Table.Message  AS Action4,
 Action12Table.Message AS Action12
FROM
 Packages AS PackageTable LEFT OUTER JOIN
  Actions AS Action0Table ON PackageTable.ID  = Action0Table.PackageID LEFT OUTER JOIN
  Actions AS Action2Table ON PackageTable.ID  = Action2Table.PackageID LEFT OUTER JOIN
  Actions AS Action4Table ON PackageTable.ID  = Action4Table.PackageID LEFT OUTER JOIN
  Actions AS Action12Table ON PackageTable.ID = Action12Table.PackageID
WHERE
 Action0Table.ActionType  = 0 AND
 Action2Table.ActionType  = 2 AND
 Action4Table.ActionType  = 4 AND
 Action12Table.ActionType = 12

Answer 1

那么为什么你不能只做一个外部JOIN,例如:

SELECT  `Package ID`, Name, `Action Type`, `Action Date`
   FROM Actions
   LEFT OUTER JOIN Packages
   ON Actions.`Package ID` = Packages.`Package ID`

？