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