Oracle 18c

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CREATE TABLE Degrees
    (Person_skey int, Degree_Code varchar2(2))
;

INSERT ALL 
    INTO Degrees (Person_skey, Degree_Code)
         VALUES (123456, 'MA')
    INTO Degrees (Person_skey, Degree_Code)
         VALUES (123456, 'JD')
SELECT * FROM dual
;



2 rows affected

CREATE TABLE CROSSWALK_TABLE
    ("DEGREE_LEVEL" varchar2(6), "DEGREE_CODE" varchar2(2), "DEGREE_HIERARCHY" int)
;

INSERT ALL 
    INTO CROSSWALK_TABLE ("DEGREE_LEVEL", "DEGREE_CODE", "DEGREE_HIERARCHY")
         VALUES ('master', 'MA', 30)
    INTO CROSSWALK_TABLE ("DEGREE_LEVEL", "DEGREE_CODE", "DEGREE_HIERARCHY")
         VALUES ('doctor', 'JD', 40)
SELECT * FROM dual
;
2 rows affected

SELECT c.DEGREE_LEVEL
FROM Degrees d
JOIN CROSSWALK_TABLE c
ON c.Degree_Code = d.Degree_Code
WHERE d.Person_skey = 123456
ORDER BY c.DEGREE_HIERARCHY DESC
FETCH FIRST  ROW ONLY


DEGREE_LEVEL


doctor