Question

declare @id int
execute getLastRaw 'subjectID','tblSubject', @id output
print @id

alter procedure getLastRaw @column char(20), @tbl Char(20),
@return int output
as
declare @dynSQL varchar(100)
select @dynSQL ='SELECT TOP 1 '+@return+'='+ @column + ' FROM ' + @tbl + ' ORDER BY ' + @column + ' DESC'
exec(@dynsQL)

I want to get the value which gets selected from the select statement. But it says:

Msg 245, Level 16, State 1, Procedure getLastRaw, Line 5
Conversion failed when converting the varchar value 'SELECT TOP 1 ' to data type int.

Answer 1

1. When you concatenate @return SQL Server tries to convert the whole expression to int because of datatype precedence

2. You can’t assign @return outside or inside of the dynamic SQL because of scope: the stored proc and the dynamic SQL are different. Local variables are local to the scope only

You’ll have to use a temp table: this is per connection and available for inner scopes (dynamic SQL)

...
declare @dynSQL varchar(100)

select @dynSQL ='SELECT TOP 1 '+ @column + ' FROM ' + @tbl + ' ORDER BY ' + @column + ' DESC'

CREATE TABLE #result (rtn int)

INSERT #result (rtn)
exec(@dynsQL)

SELECT @return = rtn FROM #result
GO

Although, it is just as easy and more correct to use a proper SELECT…

declare @id int
SELECT @id = subjectID FROM tblSubject ORDER BY subjectID DESC
print @id