Substr, regexp & clean-up

Question

Hallo everyone,
I am loading a file with some extremely messed-up data that I am trying to 'unpick'. The basic method that I am using is the following where with (many such) if clauses, I look for some key text (here STNR:AT) and then extrapolate from there where the core information is.
In the example below I find the text and then take the 'AT' and the remainder of the string ...
if INSTR(p_POSTEXT, 'STNR:AT', 1) > 0 then
     RetVal := SUBSTR(p_POSTEXT, INSTR(p_POSTEXT, 'STNR:AT', 1) + 5);
end if;
This works fine but will be a lot of effort to program and so I am looking for short-cuts.
The first thing I am wondering is whether I can 'preserve' the value returned by the if-clause call and use this value in the processing (to get RelVal) without having to call INSTR a second time. I know how to do this is VBA but am not sure of the syntax in PL/SQL.
The second thing, I was thinking might help is the use of regular expression (regexp) processing but cannot see what advantage this would give me over SUBSTR and INSTR.
Anyway, if anyone has any help for me with this, then that would be a great help.
Regards and thanks,
Alan Searle

Answer 1

Hi Michael,
Many thanks for the tip and, yes, I took a deep look at 'REGEXP' and found a whole stack of features that I could use. In the end I came up with this code below which really simplified matters for me.
Regards and many thanks,
Alan.
CREATE OR REPLACE FUNCTION fnc_at_bearb(p_POSTEXT varchar) RETURN VARCHAR AS
PRAGMA AUTONOMOUS_TRANSACTION;
strATNR varchar2(255);
numStart number;
numEnd number;
strRetVal varchar2(255);
BEGIN
numStart := REGEXP_INSTR(p_POSTEXT, 'AT', 1, 1, 1);
if numStart = 0 Then
     numStart := REGEXP_INSTR(p_POSTEXT, 'STOERANF.NR.|STNR:AXT|STOENR|STOENR|STOERNR|STOEM|STNR|STBNR|STOE|SNR', 1, 1, 1);
end if;
if numStart > 0 then
     numEnd := REGEXP_INSTR(p_POSTEXT, '[[:digit:]]+', numStart, 1, 1);
     strATNR := TRIM(REGEXP_REPLACE(SUBSTR(p_POSTEXT, numStart, numEnd - numStart), '[[:punct:]]', Null));
     strRetVal := SUBSTR(SUBSTR('AT000000000000000', 1, 15 - LENGTH(strATNR)) || strATNR, 1, 15);
else
strRetVal := numStart;
end if;
RETURN strRetVal;
END;
/