Question

我需要创建一个在SQL Server实例的所有数据库上执行的查询。另一个约束是，查询只能在包含带有特殊列的特殊表的数据库上执行。背景是在某些数据库中，特殊表（没有）具有特殊列。

基于this solution，到目前为止，我只有一个查询，该查询仅在包含特定表的数据库上执行。

SELECT *
FROM sys.databases
WHERE DATABASEPROPERTY(name, 'IsSingleUser') = 0
    AND HAS_DBACCESS(name) = 1
    AND state_desc = 'ONLINE'
    AND  CASE WHEN state_desc = 'ONLINE' 
              THEN OBJECT_ID(QUOTENAME(name) + '.[dbo].[CERTAIN_TABLE]', 'U')
         END IS NOT NULL

但是，仍然缺少的约束条件是查询只能选择表CERTAIN_TABLE具有特定列的数据库。如何实现？

Answer 1

为此，您将需要一些循环或动态sql。我真的不喜欢循环，所以这里是如何使用动态sql做到这一点。

declare @TableName sysname = 'CERTAIN_TABLE'
    , @ColumnName sysname = 'CERTAIN_COLUMN'

declare @SQL nvarchar(max) = ''

select @SQL = @SQL + 'select DatabaseName = ''' + db.name + ''' from ' + QUOTENAME(db.name) + '.sys.tables t join ' + QUOTENAME(db.name) + '.sys.columns c on c.object_id = t.object_id where t.name = ''' + QUOTENAME(@TableName) + ''' and c.name = ''' + QUOTENAME(@ColumnName) + '''' + char(10) + 'UNION ALL '
from sys.databases db
where db.state_desc = 'ONLINE'
order by db.name

select @SQL = substring(@SQL, 0, len(@SQL) - 9)

select @SQL 

--uncomment the line below when you are comfortable the query generated is correct
--exec sp_executesql @SQL

Answer 2

当我想遍历所有数据库时，我会像以下那样进行遍历。易于理解：

DECLARE @dbs TABLE ( dbName NVARCHAR(100) )
DECLARE @results TABLE ( resultName NVARCHAR(100) )

INSERT INTO @dbs
SELECT name FROM sys.databases

DECLARE @current NVARCHAR(100)

WHILE (SELECT COUNT(*) FROM @dbs) > 0
BEGIN
    SET @current = (SELECT TOP 1 dbName FROM @dbs)

    INSERT INTO @results
    EXEC
    (
        'IF EXISTS(SELECT 1 FROM "' + @current + '".INFORMATION_SCHEMA.COLUMNS
            WHERE TABLE_NAME = ''Target_Table_Name'' AND COLUMN_NAME = ''Target_Column_Name'')
        BEGIN
            --table and column exists, execute query here
            SELECT ''' + @current + '''
        END'
    )

    DELETE FROM @dbs
    WHERE dbName = @current
END

SELECT * FROM @results

选择所有具有特定表和特定列的数据库

2 个答案: