Compare amounts of two fields and compare it with third filed and return the result - sql

Question

I have an scenario where I need to compare amounts based on their Code type and compare that amount with another code type and return the result.
For example:
SELECT distinct P.TERM_KEY, C.Country_code, Amt.DAMT
FROM TERM P
INNER JOIN Country C ON P.TERM_KEY= C.TERM_KEY
INNER JOIN Amount Amt ON C.COU_KEY = Amt.PARENT_KEY AND Amt.PARENT_TABLE=Country
WHERE P.Term_no = 'ABCD' AND C.Country_CD IN (50, 51)
and result of this query is below:
TERM_KEY Country_code DAMT
201000000085 5000 1000.00
201000000083 5001 750.00
201000000081 5001 1000.00
201000000342 5000 1000.00
201000002340 5001 750.00
201000034733 5001 1000.00
Now I need to compare the Damt of country codes (50 and 51) with Country code 20, if Damt of country code 20 and Country Codes (50 , 51) are equal I need to report value as '5869', else if not equal I need to report value as '0000'.
I'll use the above result set in some other case condition
Example
Case
WHEN C.County = 999 and C.Contry_code = '20' AND ISNULL(CDED.DAmt,0)=0 THEN '5869'
C.County = 999 and C.Contry_code = '20' AND ISNULL(Amt.DAmt,0)!=0 THEN '0000'
end as Country_County
So CDED has to return the result set which I need to use in case. How can that be done?

Answer 1

Not sure what your data looks like or how it's related, but i would just create 2 sub-queries and join them.
select case
when ISNULL(subset_5051.DAmt,0) = ISNULL(subset_20.DAmt,0) then '5869'
else '0000'
end
from
(
SELECT distinct P.TERM_KEY, C.Country_code, Amt.DAMT
FROM TERM P
INNER JOIN Country C ON P.TERM_KEY= C.TERM_KEY
INNER JOIN Amount Amt ON C.COU_KEY = Amt.PARENT_KEY AND Amt.PARENT_TABLE=Country
WHERE P.Term_no = 'ABCD' AND C.Country_CD IN (50, 51)
) as subset_5051
[left / right / inner / full] join
(
SELECT distinct P.TERM_KEY, C.Country_code, Amt.DAMT
FROM TERM P
INNER JOIN Country C ON P.TERM_KEY= C.TERM_KEY
INNER JOIN Amount Amt ON C.COU_KEY = Amt.PARENT_KEY AND Amt.PARENT_TABLE=Country
WHERE P.Term_no = 'ABCD' AND C.Country_CD IN (20)
) as subset_20
on subset_5051.[?] = subset_20.[?]
i don't know what type of join you should use, or what columns to join on, but that should get you started.