ORACLE CASE WHEN (IF문) 사용 방법

-- 기본적인 ORACLE CASE 문법
CASE
        WHEN [조건문1] THEN
        		( [조회문1] )
        WHEN [조건문2] THEN
        		( [조회문2] )
        WHEN [조건문3] THEN
        		( [조회문3] )
END


-- 사용법 예시
-- EX)
SELECT
        A.SAMPLE_ID
        , CASE
                WHEN A.SAMPLE_DIV_CD = '001' THEN
                        ( SELECT B.SAMPLE_CD FROM SMAPLE_CD_TABLE B WHERE B.SAMPLE_DIV_CD = '001' )
                WHEN A.SAMPLE_DIV_CD = '002' THEN
                        ( SELECT B.SAMPLE_CD FROM SMAPLE_CD_TABLE B WHERE B.SAMPLE_DIV_CD = '002' )
                WHEN A.SAMPLE_DIV_CD = '003' THEN
                        ( SELECT B.SAMPLE_CD FROM SMAPLE_CD_TABLE B WHERE B.SAMPLE_DIV_CD = '003' )
        END AS SAMPLE_CD
FROM
        SAMPLE_TABLE_1 A