SQLD CBT 기출문제 예상문제 894번

다음 문제를 풀어보세요.

다음 중 각 거래일(STOCK_DATE) 기준으로 당일을 포함한 최근 3일간의 종가(CLOSE_PRICE) 이동평균을 구하는 SQL로 가장 적절한 것을 고르시오. (단, 이전 데이터가 3일 미만인 날은 존재하는 데이터만으로 평균을 계산한다.)

[테이블 구조]
CREATE TABLE DAILY_STOCK (
  STOCK_DATE VARCHAR(8),
  CLOSE_PRICE INT
);

SELECT STOCK_DATE, CLOSE_PRICE, 
       AVG(CLOSE_PRICE) OVER (ORDER BY STOCK_DATE ROWS BETWEEN 2 PRECEDING AND CURRENT ROW) AS MOV_AVG 
FROM DAILY_STOCK;

SELECT STOCK_DATE, CLOSE_PRICE, 
       AVG(CLOSE_PRICE) OVER (ORDER BY STOCK_DATE ROWS BETWEEN 3 PRECEDING AND CURRENT ROW) AS MOV_AVG 
FROM DAILY_STOCK;

SELECT STOCK_DATE, CLOSE_PRICE, 
       AVG(CLOSE_PRICE) OVER (ORDER BY STOCK_DATE ROWS BETWEEN CURRENT ROW AND 2 FOLLOWING) AS MOV_AVG 
FROM DAILY_STOCK;

SELECT STOCK_DATE, CLOSE_PRICE, 
       AVG(CLOSE_PRICE) OVER (PARTITION BY STOCK_DATE ORDER BY STOCK_DATE ROWS BETWEEN 2 PRECEDING AND CURRENT ROW) AS MOV_AVG 
FROM DAILY_STOCK;