multiple sql update w/ major time issues - Mailing list pgsql-sql

I have a sql update statement that is dealing with hundreds of
thousands of records.  It takes hours and hours to complete (if it
does complete and not take down the server).  Here is how I have it
right now:

update aud_member_ext_attributes b
set EXTVALUE217 = (select a.MTDfrom gl_totals awhere a.category = 'tankrent' and a.CUST_NO = b.EXTVALUE101 and
a.DIST_NO= b.EXTVALUE102 and a.SUB_NO = b.EXTVALUE105 and a.FUEL_TYPE = b.EXTVALUE123);
 

update aud_member_ext_attributes b
set EXTVALUE223 = (select a.YTDfrom gl_totals awhere a.category = 'tankrent' and a.CUST_NO = b.EXTVALUE101 and
a.DIST_NO= b.EXTVALUE102 and a.SUB_NO = b.EXTVALUE105 and a.FUEL_TYPE = b.EXTVALUE123);
 
update aud_member_ext_attributes b
set EXTVALUE229 = (select a.R12from gl_totals awhere a.category = 'tankrent' and a.CUST_NO = b.EXTVALUE101 and
a.DIST_NO= b.EXTVALUE102 and a.SUB_NO = b.EXTVALUE105 and a.FUEL_TYPE = b.EXTVALUE123);    
 

There are 3 "extvaluexxx" that are set for each "category" for a total
of 9 categories.  This makes a grand total of 27 update statements. 
Any suggestions?  It would be much appreciated!!!!!