Sql greatest,decode,instr. minimize code lines sql

Question

I did not write this code and please excuse me for my
beginner questions?
· Is there a way to make this code cleaner. Code it
where its less lines of code?
· Can we make the 2 conditions separate rather than a
one after the other?
For ex. Not like this WHEN
INSTR(CASESTAB_1.CASENOTXT,'-ll’) > 0 THEN
decode(CASESTAB_1.RECDT,NULL,TO_DATE('01/01/1900','mm/dd/yyyy'),CASESTAB_1.RECDT)
· why is it in a pair like this:
WHEN INSTR(CASESTAB_1.CASENOTXT,'-ll’) > 0 THEN
decode(CASESTAB_1.RECDT,NULL,TO_DATE('01/01/1900','mm/dd/yyyy'),CASESTAB_1.RECDT)
if the string to find in
CASESTAB_1.CASENOTXT is independent to comparing date?
Can the string search and date be separate?
· Is the a shorter way of comparing the 4 dates.?
Alternatives
Greatest(
CASE
WHEN INSTR(CASESTAB_1.CASENOTXT,'-ll’) > 0 THEN
decode(CASESTAB_1.RECDT,NULL,TO_DATE('01/01/1900','mm/dd/yyyy'),CASESTAB_1.RECDT)
WHEN INSTR(CASESTAB_1.CASENOTXT,'-ss’) > 0 THEN
decode(ERTAB.FINERDT,NULL,TO_DATE('01/01/1900','mm/dd/yyyy'),ERTAB.FINERDT)
WHEN INSTR(CASESTAB_1.CASENOTXT,'-dd ') > 0 THEN
decode(ERTAB.PUBLICATIONDT,NULL,TO_DATE('01/01/1900','mm/dd/yyyy'),ERTAB.PUBLICATIONDT)
WHEN INSTR(CASESTAB_1.CASENOTXT,'-ff’) > 0 THEN
decode(ERTAB.PUBLICATIONDT,NULL,TO_DATE('01/01/1900','mm/dd/yyyy'),ERTAB.PUBLICATIONDT)
ELSE
decode(CASESTAB.CPDT,NULL,TO_DATE('01/01/1900','mm/dd/yyyy'),CASESTAB.CPDT)
END
,decode(CASESTAB.CPDT,NULL,TO_DATE('01/01/1900','mm/dd/yyyy'),CASESTAB.CPDT))
sql finds the suffixes from CASESTAB_1.CASENOTXT
AND
compares dates 4
· CASESTAB_1.RECDT
· ERTAB.FINERDT
· ERTAB.PUBLICATIONDT
· CASESTAB.CPDT
AND GETS THE LATER OF THE 4 DATES.
1. \find the suffix from caseN0 field/col
-ll
--ss
-dd
-ff
CASESTAB_1.CASENOTXT
2. dates to find the latest date.
· CASESTAB_1.RECDT
· ERTAB.FINERDT
· ERTAB.PUBLICATIONDT
· CASESTAB.CPDT
Using greatest function.
3. the tables are
1. ERTAB
2. CASESTAB
3. CASESTAB

Answer 1

Well, I don't know how much simpler it could get and still do
what it is designed to do. For example, the statement
WHEN INSTR(CASESTAB_1.CASENOTXT,'-ll’) > 0 THEN
decode(CASESTAB_1.RECDT,NULL,TO_DATE('01/01/1900','mm/dd/yyyy'),CASESTAB_1.RECDT)
basically means that if the CASENOTXT column contains
'-ll’, then look at the RECDT column and if it is NULL, use
the date value of '01/01/1900', otherwise use the date value in the
RECDT column.....
and so on through the other WHEN clauses in your CASE
statement. Is this what you are expecting thsi query to do?
Phil