查看 - 当两个表具有相同的列名时，选择两个表的所有字段

Question

我想创建一个选择 2 个表的所有列的视图。我必须选择所有列（我不能写列名，因为可以添加列）。

我的问题是两个表都有同名的列。而且我无法更改列名。

CREATE OR ALTER VIEW [dbo].[vwSomething]
AS
    SELECT         
        dbo.A.*,
        dbo.B.*
    FROM            
        dbo.A
    INNER JOIN      
        dbo.B ON dbo.A.AID = dbo.B.AID 
GO

Answer 1

您必须为视图列命名：

CREATE OR ALTER VIEW [dbo].[vwSomething] (c1, c2, c3, ...)
AS
SELECT         dbo.A.*,
               dbo.B.*
FROM            dbo.A
INNER JOIN      dbo.B ON dbo.A.AID = dbo.B.AID 
GO

或者

CREATE OR ALTER VIEW [dbo].[vwSomething]
AS
SELECT         dbo.A.col1 c1, dbo.A.col2 c2, ...
               dbo.B.cola ca, dbo.B.colb cb, ... 
FROM            dbo.A
INNER JOIN      dbo.B ON dbo.A.AID = dbo.B.AID 
GO

一个视图应该总是返回相同的列，即使后来有人将一列添加到它的一个基表中。

Answer 2

您需要列出列。如果重复的列名包含相同的数据，您可以使用此快捷方式获取列表：

select string_agg(column_name, ', ') within group (order by table_name, ordinal_position)
from (select c.*,
             row_numbrer() over (partition by column_name order by table_name) as seqnum
      from information_schema.columns c
      where table_name in ('A', 'B') and table_schema = 'dbo'
     ) c
where seqnum = 1;

然后您可以将该列表复制到您的查询中。

Answer 3

好的！然后不要使用Select * 并枚举您的列并为它们分配别名

SELECT a.Column1 as Alias1,b.Column1 as Alias2
FROM            dbo.A a
INNER JOIN      dbo.B b ON dbo.A.AID = dbo.B.AID 

Answer 4

视图中的列名应该始终是唯一的。您可以为您的列分配一个别名，以将其与表 A 和表 B 区分开来。如果您担心将来添加新列，那么您可以使用如下动态 SQL。

DROP TABLE IF EXISTS #TempColumDetails
CREATE TABLE #TempColumDetails ([Id]INT IDENTITY(1,1), [ColumnName] VARCHAR(500),[ColumnAlias] VARCHAR(500),[TableAlias] VARCHAR(50))

INSERT INTO #TempColumDetails
SELECT
    COLUMN_NAME AS [ColumnName], 
    COLUMN_NAME+'_'+'T1' [ColumnAlias],
    'T1' AS [TableAlias]
FROM INFORMATION_SCHEMA.COLUMNS
WHERE TABLE_NAME = 'A'
ORDER BY ORDINAL_POSITION

INSERT INTO #TempColumDetails
SELECT
    COLUMN_NAME AS [ColumnName], 
    COLUMN_NAME+'_'+'T2' [ColumnAlias],
    'T2' AS [TableAlias]
FROM INFORMATION_SCHEMA.COLUMNS
WHERE TABLE_NAME = 'B'
ORDER BY ORDINAL_POSITION


DECLARE @MaxId INT,@Count INT
SELECT @MaxId = MAX(Id) FROM #TempColumDetails

DECLARE @TSQL NVARCHAR(MAX) 
SET @TSQL = 'CREATE OR ALTER VIEW [dbo].[vwSomething]
AS
SELECT ';
SET @Count = 1;
WHILE(@Count<=@MaxId)
BEGIN
    DECLARE @ColumnName VARCHAR(500),@ColumnAlias VARCHAR(500),@TableAlias VARCHAR(50)
    SELECT @ColumnName = ColumnName, @ColumnAlias = ColumnAlias, @TableAlias = TableAlias FROM #TempColumDetails WHERE Id = @Count  
    IF(@Count = @MaxId) 
    BEGIN 
        SELECT @TSQL = @TSQL+@TableAlias+'.'+@ColumnName+' AS '+@ColumnAlias+' '
    END
    ELSE
    BEGIN
        SELECT @TSQL = @TSQL+@TableAlias+'.'+@ColumnName+' AS '+@ColumnAlias+', '       
    END
    SET @Count = @Count + 1;
END

SELECT @TSQL = @TSQL + 'FROM  dbo.A T1
JOIN      dbo.B T2 ON T1.AID = T2.AID ';

EXEC(@TSQL)