SQLD CBT 기출문제 예상문제 926번

다음 문제를 풀어보세요.

다음 보기의 INSERT 문 중 처리 결과가 다른 것을 고르시오.

[ T1 ]



ID
C1
C2
C3




1
A
B
C


2
C
D
NULL

ID	C1	C2	C3
1	A	B	C
2	C	D	NULL

INSERT INTO T2 (ID, VAL)
SELECT ID, C1 AS VAL FROM T1 UNION ALL
SELECT ID, C2 AS VAL FROM T1 UNION ALL
SELECT ID, C3 AS VAL FROM T1

INSERT INTO T2 (ID, VAL)
SELECT ID
     , CASE WHEN RN=1 THEN C1
            WHEN RN=2 THEN C2
            WHEN RN=3 THEN C3
       END  VAL
FROM  T1, (SELECT LEVEL AS RN FROM DUAL CONNECT BY LEVEL <=3 )

INSERT INTO T2 (ID, VAL)
SELECT ID, VAL
FROM   T1
UNPIVOT ( VAL FOR NAME IN (C1 AS 1 , C2 AS 2, C3 AS 3 ) )

INSERT ALL INTO T2 ( ID, VAL ) VALUES ( ID, C1 )
           INTO T2 ( ID, VAL ) VALUES ( ID, C2 )
           INTO T2 ( ID, VAL ) VALUES ( ID, C3 )
SELECT *
FROM   T1