Help with one select

Question

Hi everyone,
i have a table with three columns, where in some cases, there is NULL in name column for a specific time and for a specific id.
I need to fill the missing names, with the first previous occurence. I dont know if it possible to do so within one select.
thanks for any ideas
DATA table
id, mdate, name
15, '1.7.2008 15:00', 'A'
15, '28.7.2008 18:00', 'B'
4, '1.8.2008 15:00', 'G'
5, '1.8.2008 15:00', ''
3, '1.8.2008 18:00', 'G'
15, '5.8.2008 15:00', ''
15, '5.8.2008 17:00', ''
3, '10.8.2008 18:00', ''
15, '8.8.2008 07:00', 'F'
15, '9.8.2008 07:00', ''having data above,
for example for id = 15 i would like to fill the name column with this names.
15, '5.8.2008 15:00', 'B'
15, '5.8.2008 17:00', 'B'
15, '9.8.2008 07:00', 'F'
etc
so the result of the select should be:
15, '1.7.2008 15:00', 'A'
15, '28.7.2008 18:00', 'B'
4, '1.8.2008 15:00', 'G'
5, '1.8.2008 15:00', ''
3, '1.8.2008 18:00', 'G'
15, '5.8.2008 15:00', 'B'
15, '5.8.2008 17:00', 'B'
3, '10.8.2008 18:00', 'G'
15, '8.8.2008 07:00', 'F'
15, '9.8.2008 07:00', 'F'
select 15 as id, to_date('1.7.2008 15:00','dd.mm.yyyy hh24:mi') as mdate, 'A' as name from dual union all
select 15, to_date('28.7.2008 18:00','dd.mm.yyyy hh24:mi'), 'B' from dual union all
select 4, to_date('1.8.2008 15:00','dd.mm.yyyy hh24:mi'), 'G' from dual union all
select 5, to_date('1.8.2008 15:00','dd.mm.yyyy hh24:mi'), null from dual union all
select 3, to_date('1.8.2008 18:00','dd.mm.yyyy hh24:mi'), 'G' from dual union all
select 15, to_date('5.8.2008 15:00','dd.mm.yyyy hh24:mi'), null from dual union all
select 15, to_date('5.8.2008 17:00','dd.mm.yyyy hh24:mi'), null from dual union all
select 3, to_date('10.8.2008 18:00','dd.mm.yyyy hh24:mi'), null from dual union all
select 15, to_date('8.8.2008 07:00','dd.mm.yyyy hh24:mi'), 'F' from dual union all
select 15, to_date('9.8.2008 07:00','dd.mm.yyyy hh24:mi'), null from dual

Answer 1

Try this:
update tab t1
set t1.name = ( select t2.name
                  from tab t2
                 where t2.id = t1.id
                   and t2.mdate = ( select max( t3.mdate )
                                      from tab t3
                                     where t3.mdate < t1.mdate
                                       and t3.id = t2.id ) )
where t1.name is null;