SQL查询，MAX日期，分组依据

Question

Can someone help me with a sql query? I'm looking for the most recent date (datum). It has the same OBJID but not the same RADOMGID.

BESADR  ARSMEDEL    METOD   DATUM       FNR         BYGGID  OBJID   RADOMGID

bladv   410         spar    20040930    40014686    1       14778   13640

bladv   340         m       19860505    40014686    1       14778   1026

Thanks.

Answer 1

Do a GROUP BY , with MAX to find each OBJID's max datum:

select OBJID, max(DATUM)
from tablename
group by OBJID

If you want the whole row (with max datum), use NOT EXISTS to exclude older rows:

select *
from tablename t1
where not exists (select 1 from tablename t2
                  where t2.OBJID = t1.OBJID
                    and t2.datum > t1.datum)

Will return both rows if there's a tie.

Answer 2

all newest rows for every RADOMGID

select t1.* from yourtable t1
join (
   select radomgid, max(Datum)
   from yourtable t2
   group by radomgid
     ) on t1.radomgid = t2.radomgid 

Answer 3

If you want just the latest, assuming the table is called my_object_list

select BESADR, ARSMEDEL, METOD, max(DATUM) DATUM, 
       FNR, BYGGID, OBJID, RADOMGID
from my_object_list mol
Where Objid = '14778'
group by BESADR, ARSMEDEL, METOD, 
       FNR, BYGGID, OBJID, RADOMGID
having max(datum) = mol.datum;