SELECT deptno
, CASE deptno WHEN 10 THEN 1 WHEN 20 THEN 2 ELSE 9 END AS C1
FROM dept;

SELECT deptno
, CASE deptno WHEN 10 THEN 1 WHEN 20 THEN 2 END AS C1
FROM dept;

SELECT CASE DEPTNO WHEN '10' THEN 1 END AS C1 FROM DEPT
-- 데이터의 타입이 동일하지 않으면 에러가 발생한다.

CASE문 기본 문법
SELECT deptno
CASE
WHEN deptno >= 10 THEN 1
WHEN deptno >= 10 THEN 2
END AS C1
FROM dept;