Collecting Values Into A Variable In A Loop

Dear All,

I’m trying to collect values from a query into a single variable within a loop, like so:

WHILE condition is true
BEGIN

SET @intLoop = @intLoop + 1

@myString = @myString + ‘, ‘ + (SELECT companyName FROM @tblTheseComp WHERE id = @intLoop

END

For some reason though the @myString does not collect up the values, but will equal NULL at the end of the loop.

If however I simple do

WHILE condition is true
BEGIN

SET @intLoop = @intLoop + 1

@myString = (SELECT companyName FROM @tblTheseComp WHERE id = @intLoop
END


Then I get the last value from the query as expected.

Can anyone explain why this might be?

Thanks in advance!