通过加入 3 个表来更新 SQL [英] Update SQL by joining 3 tables
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问题描述
使用下面的表结构,我需要将行 ID 插入到批准的表中,使用位置名称作为查找值.我该怎么做?
Using the below table structure i need to insert the Line ID into the approved table, using the location name as the lookup value. How do i go about doing this?
我开始使用下面的代码,但它没有做太多.在 SQL 连接方面不是很好,因此非常感谢任何帮助.
I started off using the below code, but it doesn't do much. Not that great on SQL joins so any help is much appreciated.
UPDATE dbo.Approved
SET dbo.Approved.Groupid=dbo.Lines.ID
FROM dbo.Lines,dbo.Approved, dbo.Locations
WHERE dbo.Approved.Location = dbo.Locations.Location_Name
已批准
ID (PK) | Incident | Location | GroupID
--------------------------------------------------------
1 | Theft of luggage |Oxford Circus | Null
2 | Theft of bag |Kings Cross | Null
线
ID (PK) | Line_Name |
--------------------------
1 | Central |
2 | Northern |
3 | Circle |
地点
ID (PK) | Location_Name | LineID
---------------------------------
1 | Oxford Circus |1
2 | Kings Cross |2
3 | Victoria |3
推荐答案
这是我的建议:
UPDATE t1.Approved
SET t1.Groupid = t2.ID
FROM dbo.Approved t1
INNER JOIN dbo.Locations t2 ON t1.Location = t2.Location_Name
您不需要 Lines 表,因为您想要插入的只是 LineID 而不是 Line_Name.
You don't need the Lines table because what you want to insert, at the end is just the LineID not the Line_Name.
希望能帮到你,
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