SQL Server 2008 : cursor to retrieve and replace data - sql

Question

Maybe there's a better way about this but this has to be somewhat dynamic.
From a vb.net form I need to restore or replace data from one table to another. The two tables are identical except for a couple different columns.
First I wrote some SQL to grab the column names of the table passed in. Then through ordinal position I get only the tables I want values from. I store these tables names in a temp table.
Now I want to get those values from the backup table using the temp table column names and place them in the master table.
So I guess I suppose I need a cursor to loop through in some way.. I haven't touched a cursor since college and wow.
I'll embarrass myself and post my current code.
SET #getColCURSOR = CURSOR FOR
SELECT name
FROM #MyTempTable --created previously as table only holding column names
OPEN #getColCURSOR
FETCH NEXT FROM #getColCURSOR
INTO #columnName
WHILE ##FETCH_STATUS = 0
BEGIN
select #columnName --this variable should as a column name and change
from AUDIT_TABLE a where a.ID = 7 -- 7 is just for testing is dynamic variable
FETCH NEXT FROM #getColCURSOR
INTO #columnName
END
CLOSE #getColCURSOR
DEALLOCATE #getColCURSOR

Answer 1

I'm not going to comment on whether this could be done without a cursor, since I'm a bit lost on what you're trying to do. But one issue with your cursor is that you can't parameterize a column name in a select statement. So you'll need to replace this:
WHILE ##FETCH_STATUS = 0
BEGIN
select #columnName --this variable should as a column name and change
from AUDIT_TABLE a where a.ID = 7 -- 7 is just for testing is dynamic variable
FETCH NEXT FROM getColCURSOR
INTO #columnName
END
--with dynamic SQL like this:
DECLARE #SQL nvarchar(max)
WHILE ##FETCH_STATUS = 0
BEGIN
set #SQL =
N'select ' + QUOTENAME(#columnName) + ' from AUDIT_TABLE a where a.ID = 7'
EXEC (#SQL); --w/o brackets assumes you've calling a stored proc
FETCH NEXT FROM getColCURSOR
INTO #columnName
END
That could possibly introduce other issues, since dynamic SQL statements execute in their own scope. I'd definitely encourage you to look into whether there's a set-based solution to this, since using dynamic SQL will make this even messier, and I don't think you'll be able to escape dynamic SQL if you want to use a variable for column names.