SQL - 从多个数据库中选择

Question

我有 10 个数据库，它们都在同一个实例和架构中，具有相同的表。

希望创建一个SELECT 查询，该查询可以使用数据库名称的变量并将所有记录返回到单个数据集中。

我一直在环顾四周并将以下内容放在一起作为测试（真正的 select 语句要大得多，有多个连接）

这个测试确实有效，但它返回两个结果集，每个数据库一个。

有没有办法将结果合并到一个集合中，还是我使用了错误的方法？

提前致谢

DECLARE @DB_NAME VARCHAR(6);

DECLARE CURSOR_ALLDB_NAMES CURSOR FOR 
    SELECT name
    FROM sys.databases
    WHERE name IN ('CN2DAT', 'AU1DAT') 

OPEN CURSOR_ALLDB_NAMES

FETCH NEXT FROM CURSOR_ALLDB_NAMES INTO @DB_NAME

WHILE @@Fetch_Status = 0
BEGIN
    EXEC ('SELECT * FROM ' + @DB_NAME + '.dbo.ICITEM')

    -- EXEC ('USE '+ @DB_NAME + ' SELECT * from dbo.ICITEM')

    FETCH NEXT FROM CURSOR_ALLDB_NAMES INTO @DB_NAME
END

CLOSE CURSOR_ALLDB_NAMES
DEALLOCATE CURSOR_ALLDB_NAMES

Answer 1

我会创建一个结合了选择语句的视图。例如

CREATE VIEW v_ICITEM
AS
SELECT * FROM CN2DAT.dbo.ICITEM
UNION ALL 
SELECT * FROM AU1DAT.dbo.ICITEM
go;

您也可以将源数据库作为一列包含：

CREATE VIEW v_ICITEM
AS
SELECT 'CN2DAT' AS Db, * FROM CN2DAT.dbo.ICITEM
UNION ALL 
SELECT 'AU1DAT', * FROM AU1DAT.dbo.ICITEM
go;

Answer 2

将结果存储到临时表中，例如：

CREATE TABLE #TempICITEM 
    ([DbName] [varchar](6) NOT NULL,
    [ICITEMId] [uniqueidentifier] NOT NULL,
    [Name] [varchar](100) NOT NULL,
    [Description] [varchar](1000) NOT NULL)

将您的 TSQL 选择更改为 Insert Into #TempTable Select，例如：

EXEC ('INSERT INTO #TempICITEM ([DbName],[ICITEMId],[Name],[Description]) SELECT ''' + @DB_NAME + ''' DbName,[DbName],[ICITEMId],[Name],[Description] FROM ' + @DB_NAME + '.dbo.ICITEM')

然后从临时表的组合结果中选择，例如：

SELECT * From #TempICITEM

一起来：

CREATE TABLE #TempICITEM 
    ([DbName] [varchar](6) NOT NULL,
    [ICITEMId] [uniqueidentifier] NOT NULL,
    [Name] [varchar](100) NOT NULL,
    [Description] [varchar](1000) NOT NULL)

DECLARE @DB_NAME VARCHAR(6);
DECLARE CURSOR_ALLDB_NAMES CURSOR FOR 
SELECT name
FROM sys.databases
WHERE name IN ('CN2DAT', 'AU1DAT') 

OPEN CURSOR_ALLDB_NAMES
FETCH NEXT FROM CURSOR_ALLDB_NAMES INTO @DB_NAME
WHILE @@Fetch_Status = 0
BEGIN
EXEC ('INSERT INTO #TempICITEM ([DbName],[ICITEMId],[Name],[Description]) SELECT ''' + @DB_NAME + ''' DbName,[DbName],[ICITEMId],[Name],[Description] FROM ' + @DB_NAME + '.dbo.ICITEM')
FETCH NEXT FROM CURSOR_ALLDB_NAMES INTO @DB_NAME
END

CLOSE CURSOR_ALLDB_NAMES
DEALLOCATE CURSOR_ALLDB_NAMES

SELECT * From #TempICITEM