SQL, How to Concatenate results?

Question

I currently have a SQL query that returns a number of fields. I need one f the fields to be effectively a sub query sub that.

The Problem in detail:

Answer 1

This one automatically excludes the trailing comma, unlike most of the other answers.

DECLARE @csv VARCHAR(1000)

SELECT @csv = COALESCE(@csv + ',', '') + ModuleValue
FROM Table_X
WHERE ModuleID = @ModuleID

(If the ModuleValue column isn't already a string type then you might need to cast it to a VARCHAR.)