T-SQL 查询出错 exec 不在表中

Question

我正在尝试构建一个查询，将他的输出放在一个表中。 exec(@inloop_query) 不知道之前声明的表。 （------------------之间的那部分 这是可能的还是我尝试做一些不起作用的事情？ 请指教。

（我遇到的错误是：必须声明表变量“@inloop_table”。严重性 15 状态 2）

DECLARE @frame_db_name VARCHAR(max)
DECLARE @frame_db_id INT
DECLARE @frame_table TABLE (
    db_id INT , 
    names VARCHAR(max))
DECLARE @frame_count INT
DECLARE @frame_count_max INT
SET @frame_count = 1
SET @frame_count_max = 0
SELECT @frame_count_max = count (name) FROM sys.databases WHERE Name LIKE     'B%' and state_desc = 'online' 
INSERT INTO @frame_table SELECT database_id , name FROM sys.databases     WHERE Name LIKE 'B%' and state_desc = 'online' ORDER BY database_id

DECLARE @inloop_query VARCHAR(max)
DECLARE @Inloop_table TABLE (
    IL_SchemaName VARCHAR(max) , 
    IL_TableName VARCHAR(max) , 
    IL_IndexName VARCHAR(max) , 
    IL_IndexID INT , 
    IL_Fragment INT) 

IF @frame_count_max  <= 0  
    PRINT '@count_max (<=0) = ' + CAST(@frame_count_max AS VARCHAR)
ELSE 
    WHILE @frame_count <= @frame_count_max
        BEGIN
            SELECT @frame_db_name = names , @frame_db_id = db_id FROM     @frame_table WHERE db_id IN (SELECT TOP 1 db_id FROM @frame_table ORDER BY db_id) 
        PRINT '@count_max (>=0) = ' + CAST(@frame_count_max AS VARCHAR)
        PRINT '@count = ' + CAST(@frame_count AS VARCHAR(max)) 
        PRINT 'current DB name = ' + CAST(@frame_db_name AS VARCHAR(max))
        PRINT 'current DB ID = ' + CAST(@frame_db_id AS VARCHAR(max))
        ------------------------------------------------------------ 
        SET @inloop_query = '
            USE ' + CAST(@frame_db_name AS VARCHAR(max)) + 
            ' INSERT INTO @inloop_table 
                SELECT SCHEMA_NAME(o.schema_id)     AS SchemaName,
                OBJECT_NAME(a.object_id)     AS TableName,
                i.name                       AS IndexName,
                a.index_id                   AS IndexID,
                convert(tinyint,a.avg_fragmentation_in_percent) AS [Fragment]
            FROM   sys.dm_db_index_physical_stats (DB_ID(), NULL, NULL,NULL, ''LIMITED'') AS a
                INNER JOIN sys.indexes i ON i.index_id = a.index_id
                    AND i.object_id = a.object_id 
                INNER JOIN sys.objects o ON a.object_id = o.object_id
            ORDER BY SchemaName, TableName, IndexID'
        EXEC(@inloop_query)
        ------------------------------------------------------------ 
        SET @frame_count = @frame_count + 1
        DELETE FROM @frame_table WHERE db_id IN (SELECT TOP 1 db_id FROM @frame_table ORDER BY db_id) 
    END

Answer 1

@inloop_table 在 @inloop_query 之外声明；当后者被执行时，它不知道这个变量。使用实际的表格怎么样？

/* comment this out:
DECLARE @inloop_query VARCHAR(max)
DECLARE @Inloop_table TABLE (
    IL_SchemaName VARCHAR(max) , 
    IL_TableName VARCHAR(max) , 
    IL_IndexName VARCHAR(max) , 
    IL_IndexID INT , 
    IL_Fragment INT)
*/
-- Create an auxiliary table
CREATE TABLE InLoop_Table (
        IL_SchemaName VARCHAR(max) , 
    IL_TableName VARCHAR(max) , 
    IL_IndexName VARCHAR(max) , 
    IL_IndexID INT , 
    IL_Fragment INT
);
-- ... And use this table in your dynamic sql:
SET @inloop_query = '
        USE ' + CAST(@frame_db_name AS VARCHAR(max)) + 
        ' INSERT INTO InLoop_Table ...

-- Finally, clean up:
DROP TABLE InLoop_Table;

Answer 2

表变量的范围是特定于批处理的，因此由于您的动态 sql 作为新批处理执行，因此它超出了范围并且无法识别。您当然可以在动态 sql 中声明它，但这毫无意义，因为您以后无法访问它。你有两个不错的选择：

你可以把insert放到sql外面，例如

DECLARE @inloop_query NVARCHAR(MAX) = 'USE Master; SELECT 1, 2, 3;';
DECLARE @inloop_table TABLE (A INT, B INT, C INT);

INSERT @inloop_table
EXEC(@inloop_query);

SELECT * FROM @inloop_table;

或者您可以使用临时表，而不是表变量。临时表具有会话范围，因此仍可通过EXEC() 识别：

CREATE TABLE #inloop_table (A INT, B INT, C INT);
DECLARE @inloop_query NVARCHAR(MAX) = 'USE Master; INSERT #inloop_table SELECT 1, 2, 3;';

EXEC(@inloop_query);

SELECT * FROM #inloop_table;

我还建议使用正确声明的游标，而不是使用WHILE 循环遍历表变量。这里的关键方面是正确定义的。人们通常只使用DECLARE .. CURSOR FOR SELECT..，与告诉光标您不会进行更新、不会向后移动等相比，默认选项要慢得多且占用更多内存。

DECLARE DBCursor CURSOR LOCAL STATIC FORWARD_ONLY READ_ONLY
FOR
SELECT  database_id , name 
FROM sys.databases     
WHERE Name LIKE 'B%' and state_desc = 'online' 
ORDER BY database_id;

OPEN DBCursor;
FETCH NEXT FROM DBCursor INTO @frame_db_id, @frame_db_name;

WHILE @@FETCH_STATUS = 0
BEGIN
    -- DO WHATEVER YOU NEED WITH EACH DB

    FETCH NEXT FROM DBCursor INTO @frame_db_id, @frame_db_name;
END

CLOSE DBCursor;
DEALLOCATE DBCursor;

最后一条评论是，我总是更喜欢sp_executesql 而不是EXEC() 和this article pretty much covers why，在这种情况下并没有太大区别，但值得注意。