SQLD CBT 기출문제 예상문제 857번

다음 문제를 풀어보세요.

다음 중 아래 SQL 문장들 중 오류 없이 정상적으로 실행되는 SQL로 가장 적절한 것을 고르시오.

[테이블 구조]
-- CUSTOMERS_A
CREATE TABLE CUSTOMERS_A (
    CUST_ID VARCHAR2(10),
    CUST_NAME VARCHAR2(50),
    GRADE NUMBER
);

-- CUSTOMERS_B
CREATE TABLE CUSTOMERS_B (
    CUST_ID VARCHAR2(10),
    CUST_NAME VARCHAR2(50),
    JOIN_DATE DATE
);

SELECT CUST_ID, CUST_NAME, GRADE FROM CUSTOMERS_A
UNION
SELECT CUST_ID, CUST_NAME, JOIN_DATE FROM CUSTOMERS_B;

SELECT CUST_ID, GRADE FROM CUSTOMERS_A
UNION
SELECT CUST_ID, JOIN_DATE FROM CUSTOMERS_B;

SELECT CUST_ID, CUST_NAME, TO_CHAR(GRADE) AS INFO FROM CUSTOMERS_A
UNION
SELECT CUST_ID, CUST_NAME, TO_CHAR(JOIN_DATE, 'YYYYMMDD') FROM CUSTOMERS_B;

SELECT CUST_ID, CUST_NAME FROM CUSTOMERS_A
UNION
SELECT CUST_ID, CUST_NAME, GRADE FROM CUSTOMERS_B;