存储过程执行期间无效的列名错误

Question

I am not able to execute the stored procedure. It is throwing an error

Invalid Column name 'DW201401'

Command used to execute the stored procedure:

exec RM_UTIL_MODE server,'DW201401'

Stored procedure code:

ALTER Procedure [dbo].[RM_UTIL_MODE]
    @ServerName varchar(50),
    @Value varchar(50) 
As
Begin
   declare @query nvarchar(max) 

   set @query = N'SELECT mode FROM ' + @ServerName + 
                N'.master.dbo.sysdatabases WHERE name =' + @Value

   exec sp_executesql @query
End

But when I tried to run the query alone as shown below it is giving me result.

select mode, name 
from server.master.dbo.sysdatabases 
where name = 'DW201401'

Answer 1

Presumably, the issue is quotes around @Value :

declare @query nvarchar(max) 
set @query = N'SELECT mode FROM ' 
+ @ServerName
+ N'.master.dbo.sysdatabases
WHERE name = '''+@Value+'''';

However, I would use parameter substitution instead:

declare @query nvarchar(max) ;

set @query = N'SELECT mode
FROM ' + @ServerName + N'.master.dbo.sysdatabases
WHERE name = @value';

exec sp_executesql @query, N'@value varchar(50)', @value = @value;

You are already using sp_executesql , so you might as well use it properly. Note: you cannot substitute the server name.

EDIT:

To elaborate on the comment, I would write the code this way:

    declare @sql nvarchar(max) ;

    set @sql = N'
SELECT mode
FROM @ServerName.master.dbo.sysdatabases
WHERE name = @value';

    set @sql = replace(@sql, '@ServerName', quotename(@ServerName));

    exec sp_executesql @sql, N'@value varchar(50)', @value = @value;

When using dynamic SQL, I no longer piece together the query using string concatenation. Instead, I put in place holders and use replace() . I find that concatenation is hard to maintain and often obscures what the SQL is doing. Although there is a bit more overhead in using replace() (and I often do it multiple times), it is worth it for preventing errors and maintaining the code (plus, my queries tend to run for a while anyway, so the overhead is minimal compared to the query time).

Answer 2

Your select looks like:

select mode, name from server.master.dbo.sysdatabases where name = DW201401

so you need to add escaped quotes in your dynamic query:

exec RM_UTIL_MODE cefmtqcfindv3,'DW201401'

ALTER Procedure [dbo].[RM_UTIL_MODE]
@ServerName varchar(50),@Value varchar(50) 
As

Begin

declare @query nvarchar(max) 
set @query = N'SELECT mode FROM ' 
+ @ServerName
+ N'.master.dbo.sysdatabases
WHERE name ='''+@Value+''''

exec sp_executesql @query

End

Just as a suggestion, when you are building a dynamic sql, try using PRINT instead of EXEC , then get what is printed and try it out. Most of the times you will know what went wrong.

Just as an example:

ALTER Procedure [dbo].[RM_UTIL_MODE]
@ServerName varchar(50),@Value varchar(50) 
As

Begin

declare @query nvarchar(max) 
set @query = N'SELECT mode FROM ' 
+ @ServerName
+ N'.master.dbo.sysdatabases
WHERE name ='''+@Value+''''

PRINT @query

--exec sp_executesql @query

End