계층적 데이터 JOIN LEFT

SELECT T2.POSTECHNM FROM JOBCODTBL AS T1 -- 댑스2.가져올 컬럼명
LEFT JOIN JOBCODTBL AS T2 ON T2.PARENTSNO = T1.CODESLNUM
WHERE T2.PARENTSNO = 47;	-- 댑스2.가져올 부모 인덱스 넘버

SELECT T3.POSTECHNM FROM JOBCODTBL AS T1
LEFT JOIN JOBCODTBL AS T2 ON T2.PARENTSNO = T1.CODESLNUM
LEFT JOIN JOBCODTBL AS T3 ON T3.PARENTSNO = T2.CODESLNUM
WHERE T3.PARENTSNO = 2