Case Statement or Formula for creating a flag

User2021

I have to create a flag in a dataset where

(IF columns A.a and B.a = A.b and B.b ) then I have to check cols A.c = B.c or A.d = B.d

My Data is like

Can someone help me in case statement. The one I have is not showing correct results. First two columns have to match to figure out discrepancies in next cols. If cols match it is 1 and if c and d cols are not matching then its 0.

GrantSmith

CASE WHEN `A.a` = `B.a` AND `A.b` = `B.b` THEN
  CASE WHEN `A.c` = `B.c` AND `A.d` = `B.d` THEN 1 ELSE 0 END
END

This will return NULL if A.a and A.b do not equal B.a and B.b resepctively.

1 if c and d match and a and b match

0 if they don't but a and b match