基于查询结果的动态 FROM 源

Question

我有一个包含多个数据库的 SQL Server 实例。每个数据库都有一个用户表。我正在尝试编写一个查询来计算每个数据库的用户记录数。我已经到了可以将所有database_name、schema_name 和table_name 选择到临时表中的地步。我需要能够从该查询的结果中进行选择，但我不知道该怎么做。

DECLARE @sql nvarchar(max);

SELECT @sql = 
    (SELECT ' UNION ALL
        SELECT ' +  + quotename(name,'''') + ' as database_name,
               s.name COLLATE DATABASE_DEFAULT
                    AS schema_name,
               t.name COLLATE DATABASE_DEFAULT as table_name 
               FROM '+ quotename(name) + '.sys.tables t
               JOIN '+ quotename(name) + '.sys.schemas s
                    ON s.schema_id = t.schema_id'
    FROM sys.databases 
    WHERE state = 0
    ORDER BY [name] FOR XML PATH(''), type).value('.', 'nvarchar(max)');

SET @sql = stuff(@sql, 1, 12, '') + ' order by database_name, 
                                               schema_name,
                                               table_name';

DECLARE @allTables TABLE 
                   (
                        database_name NVARCHAR(MAX), 
                        schema_name NVARCHAR(MAX), 
                        table_name NVARCHAR(MAX)
                   )

INSERT INTO @allTables 
    EXEC (@sql)

SELECT
    *
--    ,(select count(*) from [database_name].[schema_name].[table_name] where isadmin = 0) as 'Users'
--    ,(select count(*) from [database_name].[schema_name].[table_name] where isadmin = 1) as 'Admins'
FROM
    @allTables 
WHERE
    table_name = 'C2_SEC_USERS'

这会产生以下结果集：

我已经注释掉了我需要实际计算用户数的选择部分，因为它不是有效的 SQL。是否可以根据结果集选择FROM？如果有，怎么做？

Answer 1

你快到了。现在你需要做两件事 -

首先在表变量@allTables 中添加一个标识字段，如下所示

DECLARE @allTables TABLE
(
    id  int identity(1,1),
    database_name NVARCHAR(MAX), 
    schema_name NVARCHAR(MAX), 
    table_name NVARCHAR(MAX)
 )

二次构建动态查询并执行

DECLARE 
    @CurrentId      AS INT = 0,
    @CurrentDb      AS NVARCHAR(MAX),
    @CurrentSchema  AS NVARCHAR(MAX);

SET @sql = '';

WHILE (EXISTS(SELECT id FROM @allTables WHERE table_name = 'C2_SEC_USERS' AND id > @CurrentId))
BEGIN
    SELECT TOP 1 @CurrentId = id, @CurrentDb = [database_name], @CurrentSchema = [schema_name] FROM @allTables WHERE table_name = 'C2_SEC_USERS' AND id > @CurrentId
    SET @sql += CONCAT('SELECT ''', @CurrentDb, ''' ''database'', COUNT(*) ''User Count'' FROM ', @CurrentDb,'.',@CurrentSchema,'.C2_SEC_USERS');
    SET @sql += '
';
END;

EXEC (@sql)

Answer 2

我最终通过使用光标解决了这个问题

declare @sql nvarchar(max);
declare @allTables TABLE (database_name NVARCHAR(MAX), schema_name NVARCHAR(MAX), table_name NVARCHAR(MAX))
select @sql = 
    (select ' UNION ALL
        SELECT ' +  quotename(name,'''') + ' as database_name,
               s.name COLLATE DATABASE_DEFAULT
                    AS schema_name,
               t.name COLLATE DATABASE_DEFAULT as table_name 
               FROM '+ quotename(name) + '.sys.tables t
               JOIN '+ quotename(name) + '.sys.schemas s
                    on s.schema_id = t.schema_id'
    from sys.databases
    where state=0
    order by [name]
    for xml path(''), type).value('.', 'nvarchar(max)');
set @sql = stuff(@sql, 1, 12, '') + ' order by database_name, schema_name, table_name';

insert @allTables
exec (@sql)

declare @userCounts TABLE (database_name NVARCHAR(MAX),
    users int,
    admins int)
DECLARE @dbName VARCHAR(MAX)
DECLARE @schemaName VARCHAR(MAX)
DECLARE @tableName VARCHAR(MAX)
DECLARE @countSql NVARCHAR(MAX)
DECLARE tables_cursor CURSOR FOR SELECT database_name, schema_name, table_name
FROM @allTables
where table_name = 'C2_SEC_USERS' and database_name != 'master'

OPEN tables_cursor
FETCH NEXT FROM tables_cursor INTO @dbName, @schemaName, @tableName
WHILE @@FETCH_STATUS = 0 BEGIN
    set @countSql = 'Select ''' + @dbName + ''' as database_name, (select count(*) from [' + @dbName + '].dbo.C2_SEC_USERS where isadmin = 0 and isinactive = 0) as users, (select count(*) from [' + @dbName + '].dbo.C2_SEC_USERS where isadmin = 1 and isinactive = 0) as admins'
    INSERT INTO @userCounts
    exec (@countSql)
    FETCH NEXT FROM tables_cursor INTO @dbName, @schemaName, @tableName;
END;
CLOSE tables_cursor;
DEALLOCATE tables_cursor;
select * from @userCounts;