Use of SUBSTR function

Question

Hi,
I have a query like this:
SELECT decode((select count(1) from patient_history b where (b.studyid =a.studyid and b.baseline_no= a.baseline_no and b.aeseq=a.aeseq and release_date IS not NULL)),0,'New','Current') status , a.*
FROM patient_history a
In this query for the where clause ( "b.studyid =a.studyid and b.baseline_no= a.baseline_no and b.aeseq=a.aeseq")
All the columns listed here in the where clause need to come from some table tab100 which has a column named 'col'.
tab100
col
This col columns store the column names which need to used in the "where" clause comparison.(its a self join)
Say this columns has, 'STUDYID,BASLINE_NO,AESEQ" as value then how can I write a dynamic string so I can select these values as "a." or "b." etc and write the query completely.
select decode((select count(1) from patient_history || 'b' || 'WHERE( ' || ' dynamic string after fetching from col ' ||...etc.
I tried using subtsr but failed to do so. Please help.
Rgds,
Aashish

Answer 1

Hi,
This may help
-- Created on 1/19/2010 by USER
declare
  -- Local variables here
  i integer;
  str varchar2(2000);
  str1 varchar2(2000);
begin
  -- Test statements here
for i in 1..3 loop /* count of columns */
for x in (select col from test100) loop
str:=str||' a.'||REGEXP_SUBSTR(x.col, '[^,]+', 1,i)||'=b.'||REGEXP_SUBSTR(x.col, '[^,]+', 1,i)||' and';
end loop;
end loop;
str:=rtrim(str,' and');
dbms_output.put_line(str);
end;The only thing you will have to determins is the number of column you need to join.
If you are on 11g you may use regexp_count and determins else tehre are number of ways to do that you can search on teh forum.
Regards,
Bhushan
Edited by: Buga on Jan 19, 2010 9:57 AM
Included the table