-- answer
SELECT BOARD_ID,
WRITER_ID,
TITLE,
PRICE,
CASE
WHEN (STATUS = 'SALE') THEN '판매중'
WHEN (STATUS = 'RESERVED') THEN '예약중'
ELSE '거래완료'
END AS STATUS
FROM USED_GOODS_BOARD
WHERE CREATED_DATE = '2022-10-5'
ORDER BY BOARD_ID DESC;
조건문을 설정할 때 IF문을 사용할수도 있지만
여러 조건을 겹쳐서 사용해야할 경우 CASE문을 활용하여 해결하기도 합니다
CASE WHEN (조건) THEN (리턴값) ELSE (리턴값) END AS (칼럼명)
CASE
WHEN (STATUS = 'SALE') THEN '판매중'
WHEN (STATUS = 'RESERVED') THEN '예약중'
ELSE '거래완료'
END AS STATUS