조건별로 분류하여 주문상태 출력하기

DATE_FORMAT(OUT_DATE,'%Y-%m-%d') - needed formatted outputs for the requirement 
SELECT 
    ORDER_ID, PRODUCT_ID, DATE_FORMAT(OUT_DATE,'%Y-%m-%d'),
    CASE
        WHEN OUT_DATE IS NULL THEN '출고미정' 
        WHEN DATE_FORMAT(OUT_DATE,'%Y-%m-%d') <= '2022-05-01' THEN '출고완료'
        ELSE '출고대기'
    END 출고여부 
FROM FOOD_ORDER 
ORDER BY ORDER_ID;

# enter else statement OUT_DATE IS NULL implicitly >> explicitily 
# not necessarily handle null 
SELECT ORDER_ID, PRODUCT_ID, DATE_FORMAT(OUT_DATE,'%Y-%m-%d'),
CASE
    WHEN OUT_DATE IS NULL THEN '출고미정' 
    WHEN DATE_FORMAT(OUT_DATE, '%Y-%m-%d') <= '2022-05-01' THEN '출고완료'
    WHEN DATE_FORMAT(OUT_DATE, '%Y-%m-%d') > '2022-05-01' THEN '출고대기'
    ELSE '출고미정'
END AS 출고여부 
FROM FOOD_ORDER 
ORDER BY ORDER_ID