努力在 SQL 服务器中学习 sp_executesql

Question

我正在努力自学 SQL 游标和 sp_executesql 我正在从事的项目。我想我已经很接近了，但是我没能得到我想要的东西，我希望有人能帮助我克服我缺乏知识的问题。在此先感谢您的帮助！

以下是我目前的代码（注释注释是我自言自语）：

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

查询运行没有错误（胜利），但似乎没有从 sp_executesql 子例程返回任何值。这是返回输出的示例：

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 |

我很确定我在构建要发送到 sp_executesql 的 @sqlstring 时遇到了错误，但我找不到好的资源来帮助我了解我在哪里出错了。正如我之前所说，任何帮助将不胜感激。

Answer 1

我很确定它需要像这样阅读

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

然后在您的印刷品中参考那些。您还需要添加这些声明声明@passed_element_table NVARCHAR(50) 声明@passed_element_column NVARCHAR(50)

到@sqlString

Answer 2

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

你在看内部变量。

还有：

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'

会更清楚

更清晰：

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

努力在 SQL 服务器中学习 sp_executesql

Struggling to learn sp_executesql in SQL Server

sql-server

tsql

cursor

sp-executesql