sql - SQL SELECT JOIN 列别名

Question

在此先感谢您的帮助：

[People]表有两列：

• 个人ID
• 人名

[Marriages]表有三列：

• 结婚证
• 个人身份证
• 个人IDb

我想选择以下列：

• 结婚证
• 人名（对于 personIDa）
• PersonName（用于 personIDb）

我想我需要使用SELECT带有 a 的语句JOIN，但我不确定如何为每个PersonName. 这是我到目前为止所拥有的（这不起作用）：

SELECT 
    [Marriages].[MarriageID], 
    [People].[PersonName] AS aName, 
    [People].[PersonName] AS bName  
FROM 
    [Marriages]  
JOIN 
    [People] ON [Marriages].[PersonIDa] = [People].[PersonID]  
JOIN 
    [People] ON [Marriages].[PersonIDb] = [People].[PersonID]  

再次感谢...

Answer 1

这是否符合您要完成的任务？

SELECT m.[MarriageID], peopleA.[PersonName] AS aName, peopleB.[PersonName] AS bName  
FROM [Marriages]  M
JOIN [People] peopleA ON m.[PersonIDa] = peopleA.[PersonID]  
JOIN [People] peopleB ON m.[PersonIDb] = peopleB.[PersonID]  

Answer 2

我认为您正在尝试这样做...

SELECT 
m.[MarriageID], 
pa.[PersonName] AS aName,
pb.[PersonName] AS bName  
FROM [Marriages] m
JOIN [People] pa ON m.[PersonIDa] = pa.[PersonID]  
JOIN [People] pb ON m.[PersonIDb] = pb.[PersonID];

Answer 3

您将需要类似的东西：

Select MarriageID, a.PersonName, b.PersonName
From Marriages m
Join People a On a.PersonID = m.Person1ID 
Join People b on b.PersonID = m.Person2ID 

Answer 4

不要忘记您需要什么类型的 JOIN...“INNER JOIN”/“LEFT OUTER JOIN”/“RIGHT OUTER JOIN”/“CROSS JOIN”

SELECT MarriageID, a.PersonName, b.PersonName
FROM Marriages m JOIN People a ON a.PersonID = m.Person1ID 
                 JOIN People b ON b.PersonID = m.Person2ID 

Answer 5

谢谢大家; 你的建议很有效。当我应该尝试为 JOIN 语句中的重复表创建别名时，我试图为 SELECT 语句中的重复列创建别名。

对于遇到此问题的其他任何人：

SELECT  
[TABLE1 NAME].[TABLE1 COLUMN],  
(TABLE2 ALIAS1).[TABLE2 COLUMN],  
(TABLE2 ALIAS2).[TABLE2 COLUMN],  
FROM [TABLE1 NAME]  
JOIN [TABLE2 NAME] (TABLE2 ALIAS1) ON [TABLE1 NAME].[TABLE1 MATCHING COLUMN] = (TABLE2 ALIAS1).[TABLE2 MATCHING COLUMN]  
JOIN [TABLE2 NAME] (TABLE2 ALIAS2) ON [TABLE1 NAME].[TABLE1 MATCHING COLUMN] = (TABLE2 ALIAS2).[TABLE2 MATCHING COLUMN]  

别名在 JOIN 语句中创建并应用于 SELECT 语句中使用它的位置，而不是相反。