problem with slow select - Mailing list pgsql-sql

hi 

I have two tables:

table:    XXXX
idcode varchar(15) -->references (idcode) table YYYY
latitude float
longitude float
time timestamp
p_a char(1)
barcode....
address....
idprog serial... -->primary key
flag boolean

table YYYY
idfact numeric(7,0) --->references .....
idcode varchar(15) --->primary key
name varchar(20)

I want to exctract the last operation of table XXXX for each idcode of
table YYYY where idfact=123

I HAVE THIS QUERY BUT IT IS TOO SLOW (10 SECONDS):

select XXXX.*,YYYY.name from YYYY,XXXX  join (select
XXXX.idcode,max(XXXX.tempo) as tempo from XXXX,YYYY where
YYYY.idfact=123 and XXXX.idcode=YYYY.idcode  group by XXXX.idcode)
temptable on (temptable.tempo=XXXX.tempo and
temptable.idcode=XXXX.idcode) where YYYY.idfact=123 and
XXXX.idcode=YYYY.idcode order by YYYY.name;

PLEASE HELP ME



--
francescosaf
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