SELECT ORDER_ID, PRODUCT_ID, TO_CHAR(OUT_DATE, 'YYYY-MM-DD') OUT_DATE
,CASE WHEN TO_CHAR(OUT_DATE, 'MM-DD') <= '05-01' THEN '출고완료'
WHEN TO_CHAR(OUT_DATE, 'MM-DD') > '05-01' THEN '출고대기'
ELSE '출고미정'
END 출고여부
FROM FOOD_ORDER
ORDER BY ORDER_ID;
NULL을 처리할 필요는 없었다..