Select only last date

Question

Hi all!
How do I select only last date for each contragentid?
So for contragentid = 111270 it should be only '14.05.2010'.
select dd.contragentid,
decode(dd.ratingvalue,'PK1',1,'PK2',2,'PK3',2,'PSR',2,'UN4',2,'VVL',2,'BK',4,3) as ratingvalue from
(select 36 as contragentid, 'UN1' as ratingvalue, '25.02.2010' as ratingstartdate from dual
union all
select 111270 as contragentid, 'PK1' as ratingvalue, '26.11.2009' as ratingstartdate from dual
union all
select 111270 as contragentid, 'PK3' as ratingvalue, '14.05.2010' as ratingstartdate from dual
union all
select 111270 as contragentid, 'BK' as ratingvalue, '14.06.2011' as ratingstartdate from dual ) dd
where dd.ratingstartdate <= to_date('31.05.2010', 'DD.MM.YYYY')Also I need to select all rows from second test case for those contragentid which absent in first case, it should be one statement for both cases.
select * from
(select 5 as contragentid, 2 as ratingvalue from dual
union all
select 111270 as contragentid, 1 as ratingvalue from dual ) hhThanks ahead!

Answer 1

I've got solution for the first part of my beginning post:
select dd.contragentid,
decode(dd.ratingvalue,'PK1',1,'PK2',2,'PK3',2,'PSR',2,'UN4',2,'VVL',2,'BK',4,3) as ratingvalue,
last_value(dd.ratingstartdate) over
   (partition by dd.contragentid ORDER BY dd.contragentid, dd.ratingstartdate desc 
      ROWS BETWEEN CURRENT ROW AND UNBOUNDED FOLLOWING) AS last_ratingstartdate
FROM
(select 36 as contragentid, 'UN1' as ratingvalue, to_date('25.02.2010','DD.MM.YYYY') as ratingstartdate from dual
union all
select 111270 as contragentid, 'PK1' as ratingvalue, to_date('26.11.2009','DD.MM.YYYY') as ratingstartdate from dual
union all
select 111270 as contragentid, 'PK3' as ratingvalue, to_date('14.05.2010','DD.MM.YYYY') as ratingstartdate from dual
union all
select 111270 as contragentid, 'BK' as ratingvalue, to_date('14.06.2011','DD.MM.YYYY') as ratingstartdate from dual ) dd,
(select contragentid, max(ratingstartdate) as ratingstartdate from
(select 36 as contragentid, 'UN1' as ratingvalue, to_date('25.02.2010','DD.MM.YYYY') as ratingstartdate from dual
union all
select 111270 as contragentid, 'PK1' as ratingvalue, to_date('26.11.2009','DD.MM.YYYY') as ratingstartdate from dual
union all
select 111270 as contragentid, 'PK3' as ratingvalue, to_date('14.05.2010','DD.MM.YYYY') as ratingstartdate from dual
union all
select 111270 as contragentid, 'BK' as ratingvalue, to_date('14.06.2011','DD.MM.YYYY') as ratingstartdate from dual )
where ratingstartdate <= to_date('31.05.2010', 'DD.MM.YYYY')
group by contragentid ) uu
where
    uu.contragentid = dd.contragentid
and uu.ratingstartdate = dd.ratingstartdateNow I need to add contragentid from the second test case (see beginning post) which are absent in my first test case.