Update and Select from the same table

Question

Hello,
i have this select - i tested it and its working
[code]
select
case
when DTF_REEW_201301.KTMO =1 then DTF_REEW_201301.KTBT
else DTF_REEW_201301.KTBT - CTF_REEW_KUM_201301.KTBT
end
as KTBT_ISO,
case
when DTF_REEW_201301.KTMO =1 then DTF_REEW_201301.KTZN
else DTF_REEW_201301.KTZN - CTF_REEW_KUM_201301.KTZN
end
as KTZN_ISO,
case
when DTF_REEW_201301.KTMO =1 then DTF_REEW_201301.KTAB
else DTF_REEW_201301.KTAB - CTF_REEW_KUM_201301.KTAB
end as KTAB_ISO,
DTF_REEW_201301.brnrn,
DTF_REEW_201301.ktat
   from
reewcore.CTF_REEW_KUM_201301 CTF_REEW_KUM_201301,
reewdq.DTF_REEW_201301 DTF_REEW_201301
   where
(DTF_REEW_201301.BRNRN = CTF_REEW_KUM_201301.BRNRN
and DTF_REEW_201301.KTAT = CTF_REEW_KUM_201301.KTAT)
and CTF_REEW_KUM_201301.KTMO = (DTF_REEW_201301.KTMO - 1)
[/code]
With the result from KTBT_ISO, KTZN_ISO and KTAB_ISO i want to update the table "reewdq.DTF_REEW_201301" - and this table is in the select-statement!
I believe, i tried every update-statement - but no update is working.
I need something like this:
[code]
update reewdq.DTF_REEW_201301 t1 set t1.KTBT_ISO=
select
case
when DTF_REEW_201301.KTMO =1 then DTF_REEW_201301.KTBT
else DTF_REEW_201301.KTBT - CTF_REEW_KUM_201301.KTBT
end
as KTBT_ISO
   from
reewcore.CTF_REEW_KUM_201301 CTF_REEW_KUM_201301,
reewdq.DTF_REEW_201301 DTF_REEW_201301
   where
(DTF_REEW_201301.BRNRN = CTF_REEW_KUM_201301.BRNRN
and DTF_REEW_201301.KTAT = CTF_REEW_KUM_201301.KTAT)
and CTF_REEW_KUM_201301.KTMO = (DTF_REEW_201301.KTMO - 1)
t1.KTZN_ISO=
select
case
when DTF_REEW_201301.KTMO =1 then DTF_REEW_201301.KTZN
else DTF_REEW_201301.KTZN - CTF_REEW_KUM_201301.KTZN
end
as KTZN_ISO
   from
reewcore.CTF_REEW_KUM_201301 CTF_REEW_KUM_201301,
reewdq.DTF_REEW_201301 DTF_REEW_201301
   where
(DTF_REEW_201301.BRNRN = CTF_REEW_KUM_201301.BRNRN
and DTF_REEW_201301.KTAT = CTF_REEW_KUM_201301.KTAT)
and CTF_REEW_KUM_201301.KTMO = (DTF_REEW_201301.KTMO - 1)
t1.KTAB_ISO=
select
case
when DTF_REEW_201301.KTMO =1 then DTF_REEW_201301.KTAB
else DTF_REEW_201301.KTAB - CTF_REEW_KUM_201301.KTAB
end as KTAB_ISO
   from
reewcore.CTF_REEW_KUM_201301 CTF_REEW_KUM_201301,
reewdq.DTF_REEW_201301 DTF_REEW_201301
   where
(DTF_REEW_201301.BRNRN = CTF_REEW_KUM_201301.BRNRN
and DTF_REEW_201301.KTAT = CTF_REEW_KUM_201301.KTAT)
and CTF_REEW_KUM_201301.KTMO = (DTF_REEW_201301.KTMO - 1)
[/code]
But this code isn´t working. Has someone an idea please? Can someone please help me.
Best regards
Heidi

Answer 1

Use MERGE:
merge
  into reewdq.DTF_REEW_201301 t1
  using (
         select  case
                   when DTF_REEW_201301.KTMO =1 then DTF_REEW_201301.KTBT 
                   else DTF_REEW_201301.KTBT - CTF_REEW_KUM_201301.KTBT
                 end as KTBT_ISO,
                 case
                   when DTF_REEW_201301.KTMO =1 then DTF_REEW_201301.KTZN 
                   else DTF_REEW_201301.KTZN - CTF_REEW_KUM_201301.KTZN
                 end as KTZN_ISO,
                 case
                   when DTF_REEW_201301.KTMO =1 then DTF_REEW_201301.KTAB 
                   else DTF_REEW_201301.KTAB - CTF_REEW_KUM_201301.KTAB
                 end as KTAB_ISO,
                 reewdq.ROWID as rid
           from  reewcore.CTF_REEW_KUM_201301 CTF_REEW_KUM_201301, 
                 reewdq.DTF_REEW_201301 DTF_REEW_201301
           where DTF_REEW_201301.BRNRN = CTF_REEW_KUM_201301.BRNRN
             and DTF_REEW_201301.KTAT = CTF_REEW_KUM_201301.KTAT
             and CTF_REEW_KUM_201301.KTMO = DTF_REEW_201301.KTMO - 1
        ) t2
  on (
      t1.rowid = t2.rid
  when mathed
    then
      update
         set t1.KTBT_ISO = t2.KTBT_ISO,
             t1.KTZN_ISO = t2.KTZN_ISO,
             t1.KTAB_ISO = t2.KTAB_ISO
SY.