I was a little confused.

I know you can only use whatever values are actually passed back (defined) from the CTE, I didn't know that the value remembers which row and table it came from.

I thought that:

UPDATE table1_filtered

SET t_txt = 'New Val'

I thought that the value passed back was just a value.

If you did something like:

SELECT t_id, t_txt

FROM

(

SELECT t1.t_id, t2.t_txt --This is changed to t2

FROM #table1 t1

JOIN #table2 t2 ON t1.t_id = t2.t_id

) a

The outside select doesn't actually know the tables and rows that t_id and t_txt actually come from - or does it?

Thanks,

Tom