SQL UPDATE of SELECTed records

["Steve McKay" <nospammers1@xxxxxxxxx>]

All -

My apologies for posting in the RPG group - I didn't find an SQL group.

I am trying to UPDATE several records returned by a SELECT statement but am 
getting SQL0104 (Token <END-OF-STATEMENT> was not valid. Valid tokens: < > = 
<> <= !<).

Can this be done?  Current statement looks like this:

UPDATE library/file
SET field = 'U'
WHERE
(SELECT fields
FROM library/file
WHERE conditions)

Obviously, I've left out actual library and field names plus the conditions 
that I'm testing, but you get the idea.

Thanks in advance,

Steve