destructive "SELECT" query for SQL?

[Dr. Hawkins]

I have finally figured out how to make my read/write to the remote server
UNION compatible for my various tables.  And it was so obvious that I feel
silly.

Anyway, after handing over a block of UPDATE followed by a SELECT with
UNION, I'll still have a bit of cruft in a particular column.  Ideally, I'd
like to attach something to my SELECT that sets that column to NULL as a
side effect.  It would be easy enough to do as an UPDATE at the end of the
block, but then I lose the results of my SELECTs.  It could also wait for
the next transaction without great harm.

But is there a way to do a SELECT sot that it wipes a field?
INSERT/RETURNING doesn't seem to be compatible with having a subsequent
SELECT (if I could, I could return the original argument as a string while
setting the field to NULL).

In any event, this sure beats what I had before  . . .

-- 
Dr. Richard E. Hawkins, Esq.
(702) 508-8462