不明确的列名错误，我该如何解决? [英] Ambiguous column name error, how do I fix it?

问题描述

1. Users 4 Cols
UserID - UserName - RealName - Flags

2. UsersGroups 2 Cols
UserID - GroupID

3. Groups 3 Cols
GroupID - GroupName - Flags

我想要做的是选择一个特定的用户名，即 USERA 并更新标志列.但我也想将 Groups 表中的 Flags 列更新为相同的值.

What I want to do is select a specific UserName ie USERA and update the Flags column. but I also want to update the Flags column in the Groups table to the same value.

UPDATE dbo.Users
SET Flags = @var
WHERE UserName = 'UserA'

UPDATE dbo.Groups
SET Flags = @var
FROM dbo.Users u INNER JOIN dbo.UsersGroups ug ON u.UserID = ug.UserID
INNER JOIN dbo.Groups g ON g.GroupID = ug.GroupID
WHERE u.UserName = 'UserA'

但我不断收到:不明确的列名标志".

but I keep getting : Ambiguous column name 'Flags'.

如果我设置 Groups.Flags = @Var我明白了:消息 4104，级别 16，状态 1，第 1 行无法绑定多部分标识符Groupy.Flags".

if I do Set Groups.Flags = @Var i get : Msg 4104, Level 16, State 1, Line 1 The multi-part identifier "Groupy.Flags" could not be bound.

推荐答案

您需要为 Groups 表添加别名.改变这个:

You need to add the alias for the Groups table. Change this:

UPDATE dbo.Groups
SET Flags = @var
FROM dbo.Users u INNER JOIN dbo.UsersGroups ug ON u.UserID = ug.UserID
INNER JOIN dbo.Groups g ON g.GroupID = ug.GroupID
WHERE u.UserName = 'UserA'

为此:

UPDATE g -- change dbo.Groups here to simply 'g'
SET g.Flags = @var
FROM dbo.Users u INNER JOIN dbo.UsersGroups ug ON u.UserID = ug.UserID
INNER JOIN dbo.Groups g ON g.GroupID = ug.GroupID
WHERE u.UserName = 'UserA'

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