Question

I am trying to use some dynamic sql. I have generated over 100 parameters, and to speed things up I am trying to use dynamic sql to only insert values into a table that I have to based off of information retrieved from other tables. I have tried many things like adding a cast etc.

Example of what I mean:

DECLARE @var1 NVARCHAR(MAX)

-- Loop through and add various values
SET @var1 = @var1 + @parameterName
-- The parameter name is retrieved from a table that holds this information

the problem is that when I add the parameter name which would be like “@myFirstParameter” into my final expression so something like this:

DECLARE @finalString NVARCHAR(MAX)
SET @finalString = 'INSERT INTO myTableName ([myFirstParameter]) VALUES (@myFirstParameter)'
EXEC(@finalString)

The “@myFirstParameter” does not get replaced by it’s value and I get the following error:
Must declare the scalar variable “@myFirstParameter”.

Does anyone know of a way to go from the string name of a parameter to the actual value? I am trying to avoid hardcoding all the values and any work around I have attempted has failed and given me errors which appear to be much worse than what I have stated above.

Answer 1

The first way is to add the parameter’s value, instead of its name, to the SQL string:

SET @finalString = 'INSERT INTO myTableName ([myFirstParameter]) VALUES (' + 
    @myFirstParameter + ')'

This assumes the parameter has a string value. If not, you have to cast it, like cast(@myFirstParameter as varchar(128)).

The second way is to use sp_executesql instead of exec:

exec sp_executesql 
    N'INSERT INTO myTableName ([myFirstParameter]) VALUES (@myFirstParameter)',
    N'@myFirstParameter varchar(128)',
    @myFirstParameter = @myFirstParameter;