I like that answer, thanks for sharing. I know some may find that logic hard to follow, at least some that I know. 🙂 We have always used the following code to get the first of the month. Of course you would replace the getdate() with the date from your table.

select DATEADD(dd, -(DATEPART(dd, GETDATE())) +1, convert(char(10), GETDATE(), 101))