How to do this in SQL or User defined Function?

Question

Hello All
I have a table STATUS_CODES which has values like this
HRKEY ITEMKEY
HRAS 1
HVAS 1
HXAS 1
SMST 2
SLRS 2
HWAS 2
PAYT 3
The HRKEY is unique
Same ITEMKEY may be applied to different HRKEY (Item keyhas fixed values 1, 2, 3)
Now I have a function which can return values like one of these(any combination of HRKEYseparated by a dash) which is captured in a variable called LAST_STATUS
HRAS-PAYT
HRAS-SMST-PAYT
PAYT
HRAS
HXAS
HRAS-HVAS-PAYT
HRAS-HVAS-SMST-SLRS-PAYT
HRAS-HVAS-SMST
Now I want my query or function to do this
If one of the values in the LAST_STATUS string matches STATUS_CODES.HRKEY, then it should return that HRKEY based on the priority below
If Itemkey = 1 then it should return HRKEY for ITEMKEY = 1
Then 2 and then 3
If there are more than one HRKEY for same ITEMKEY then it should return any one of them
SO for eg.
If LAST_STATUS = HRAS-HVAS-SMST-SLRS-PAYT, then Output = HRAS
If LAST_STATUS = SLRS-PAYT, then Output = SLRS
If LAST_STATUS = PAYT, then Output = PAYT
Thank you for your help
Ach

Answer 1

With Scott’s setup script …
flip@FLOP> var str varchar2(1000);
flip@FLOP> exec :str := 'HRAS-HVAS-SMST-SLRS-PAYT';
PL/SQL procedure successfully completed.
flip@FLOP>
flip@FLOP> with a as
  2       ( select :str last_status from dual )
  3      ,b as
  4       (select '-'||last_status str, rownum rn from a connect by level <= length(last_status) )
  5      ,c as
  6       (select str, rn
  7              ,instr(str,'-',1,rn  ) f
  8              ,instr(str,'-',1,rn+1) t
  9        from   b
10        where  instr(str,'-',1,rn) > 0
11       )
12      ,d as
13       ( select c.*, decode(t,0,substr(str,f+1),substr(str,f+1,t-f-1)) x
14         from  c
15       )
16      ,e as
17       (
18  select d.*, s.itemkey, row_number() over (order by s.itemkey, d.x) rnk
19  from   d, status_codes s
20  where  d.x = s.hrkey
21       )
22  select x hrkey
23  from   e
24  where  rnk = 1
25  ;
HRKEY
HRAS
flip@FLOP> exec :str := 'SLRS-PAYT'
PL/SQL procedure successfully completed.
flip@FLOP> /
HRKEY
SLRS
flip@FLOP> exec :str := 'PAYT'
PL/SQL procedure successfully completed.
flip@FLOP> /
HRKEY
PAYT
flip@FLOP> exec :str := null;
PL/SQL procedure successfully completed.
flip@FLOP> /
no rows selected
flip@FLOP> exec :str := 'HRAS-HVAS----SMST-SLRS-PAYT-HRAS-HVAS-PAYT-HRAS-HVAS-SMST-SLRS-PAYT-HRAS-HVAS-SMST-SLRS-PAYT--';
PL/SQL procedure successfully completed.
flip@FLOP> /
HRKEY
HRAS