DerAdler

I am trying to filter duplicates out in OPERATION_TYPE by 2 values (X,I). Possible choices are X, I and NULL. I want to return "I" when "X" is NULL ELSE "X". This is what I have: SELECT * FROM TABLE WHERE OPERATION_TYPE = 'X' OR OPERATION_TYPE = 'I' AND OPERATION_TYPE = 'X' IS NULL Which only gives me "I"