努力学习SQL Server中的sp_executesql

Question

我想教我自己都SQL项目和sp_executesql我正在工作的项目。我想，我很接近，但我没有得到我想要的，我希望有人能帮助我度过自己缺乏的知识。在此先感谢您的帮助！

以下是我当前的代码（注释的注解我对自己说）：

DECLARE @form_id INT 
DECLARE @element_table NVARCHAR(50) 
DECLARE @element_column NVARCHAR(50) 
DECLARE @element_id INT 
DECLARE @sqlString NVARCHAR(1000) 
DECLARE @sqlDefinition NVARCHAR(1000) 
DECLARE @outputDataType VARCHAR(50) 
DECLARE @parmRET1 VARCHAR(30) 
DECLARE @sqlresult VARCHAR(50) 
DECLARE @passed_element_table NVARCHAR(50) 
DECLARE @passed_element_column NVARCHAR(50) 

SET @form_id = 220 --- temporary value for testing 

--- this gets the list of ELEMENT_IDs for the cursor 
DECLARE db_cursor CURSOR FOR SELECT 
    ELEMENT_ID 
FROM FORM_ELEMENT fe 
WHERE fe.FORM_ID = @form_id 

--- Cursor loop starts here 
OPEN db_cursor 

FETCH NEXT FROM db_cursor INTO @element_id 

WHILE @@fetch_status = 0 
BEGIN 

--- These two SET statements get me the table name and column I want to retrieve the datatype for 
SET @element_table = (
    SELECT DISTINCT 
     mtm.MAP_TABLE_NAME 
    FROM FORM_ELEMENT fe 
    LEFT OUTER JOIN ELEMENT e 
     ON fe.ELEMENT_ID = e.ELEMENT_ID 
    LEFT OUTER JOIN FORM_DATA_MAPPING_MASTER fdmm 
     ON fe.FORM_DATA_MAPPING_ID = fdmm.FORM_DATA_MAPPING_ID 
    LEFT OUTER JOIN MAPPING_TABLE_MASTER mtm 
     ON fdmm.MAP_TABLE_ID = mtm.MAP_TABLE_ID 
    INNER JOIN FORM f 
     ON fe.FORM_ID = f.FORM_ID 
    WHERE fe.FORM_ID = @form_id 
    AND fe.ELEMENT_ID = @element_id 
) 
SET @element_column = (
    SELECT DISTINCT 
     mcm.MAP_COLUMN_NAME 
    FROM FORM_ELEMENT fe 
    LEFT OUTER JOIN ELEMENT e 
     ON fe.ELEMENT_ID = e.ELEMENT_ID 
    LEFT OUTER JOIN FORM_DATA_MAPPING_MASTER fdmm 
     ON fe.FORM_DATA_MAPPING_ID = fdmm.FORM_DATA_MAPPING_ID 
    LEFT OUTER JOIN MAPPING_COLUMN_MASTER mcm 
     ON fdmm.MAP_COLUMN_ID = mcm.MAP_COLUMN_ID 
    WHERE fe.FORM_ID = @form_id 
    AND fe.ELEMENT_ID = @element_id 
) 

--- This is where I begin building the dynamic sql. I'm unsure if I need the DECLARE statement here, if I've used it above 
SET @sqlString = N'DECLARE @sqlResult VARCHAR(50) SET @sqlResult = (SELECT DATA_TYPE FROM INFORMATION_SCHEMA.COLUMNS WHERE TABLE_NAME = @passed_element_table AND COLUMN_NAME = @passed_element_column)' 
SET @sqlDefinition = N'@passed_element_table nvarchar(50), @passed_element_column nvarchar(50), @outputDataType varchar(30) OUTPUT' 
SET @passed_element_table = @element_table 
SET @passed_element_column = @element_column 

--- This is where I execute the dynamic sql 
EXECUTE sp_executesql @sqlString 
       , @sqlDefinition 
       , @passed_element_table = @element_table 
       , @passed_element_column = @element_column 
       , @outputDataType = @sqlresult OUTPUT 

--- Here I'm just using a print statement to dump out the results of the prior SP execution 
PRINT @element_table + ' | ' + @element_column + ' | ' + 
CASE 
    WHEN @outputDataType IS NULL THEN '' 
    ELSE @outputDataType 
END 

--- This ends the loop for this element_id, and restarts the process 
FETCH NEXT FROM db_cursor INTO @element_id 

END 

--- This finishes the cursor loop, and then deallocates the cursor when there are no more element_ids 
CLOSE db_cursor 
DEALLOCATE db_cursor 

查询没有错误（胜利）中运行，但它似乎并没有得到任何值回来自sp_executesql子例程。下面是返回的输出样本：

BIOGRAPH_MASTER | BIRTH_DTE | 
BIOGRAPH_MASTER | SSN | 
BIOGRAPH_ETHNIC_RACE | RACE | 
BIOGRAPH_ETHNIC_RACE | ETHNICITY | 
NAME_MASTER | UDEF_1A_2 | 
ADDRESS_MASTER | ADDR_LINE_1 | 
ADDRESS_MASTER | ADDR_LINE_2 | 
ADDRESS_MASTER | CITY | 
ADDRESS_MASTER | STATE | 

我敢肯定，我有我如何建造的@SQLString发送到sp_executesql的错误，但我不能找到一个很好的资源，以帮助我明白我出错的地方。正如我之前所说，任何援助将不胜感激。

Answer 1

PRINT @element_table + ' | ' + @element_column + ' | ' + 
CASE 
    WHEN @SqlResult IS NULL THEN '' 
    ELSE @SqlResult 
END 

你在哪里看的内部变量。

另外：

SET @sqlString = N'DECLARE @sqlResult VARCHAR(50) SELECT @outputDataType = DATA_TYPE FROM INFORMATION_SCHEMA.COLUMNS WHERE TABLE_NAME = @passed_element_table AND COLUMN_NAME = @passed_element_column' 

会更清晰

更清晰依然：

SELECT @outputDataType = DATA_TYPE FROM INFORMATION_SCHEMA.COLUMNS WHERE TABLE_NAME = @passed_element_table AND COLUMN_NAME = @passed_element_column 

不使用sp_executesql

Answer 2

我敢肯定，这将需要阅读这样

EXECUTE sp_executesql @sqlString 
      , @sqlDefinition 
      , @element_table 
      , @element_column 
      , @sqlresult OUTPUT 

，然后打印这些参考。您还需要添加这些声明 DECLARE @passed_element_table NVARCHAR（50） DECLARE @passed_element_column NVARCHAR（50）

到@SQLString