프로그래머스_우유와 요거트가 담긴 장바구니

문제

programmers.co.kr/learn/courses/30/lessons/62284

코딩테스트 연습 - 우유와 요거트가 담긴 장바구니

풀이

DISTINCT는 중복을 제거하기 위해 사용하며 해당 컬럼에 대해서 유일한 레코드만 선택할 수 있다.

SELECT DISTINCT 컬럼명1, 컬럼명2....
FROM 테이블명
WHERE 컬럼명 IN (값1, 값2, 값3...);

SELECT SUM(DISTINCT 컬럼명1), 컬럼명2....
FROM 테이블명
WHERE 컬럼명 IN (값1, 값2, 값3...);

코드

-- WHERE
SELECT DISTINCT CART_ID
FROM CART_PRODUCTS
WHERE 
    CART_ID IN (SELECT CART_ID FROM CART_PRODUCTS WHERE NAME = "Yogurt") AND 
    CART_ID IN (SELECT CART_ID FROM CART_PRODUCTS WHERE NAME = "Milk")
ORDER BY CART_ID;

-- INNER JOIN(1)
SELECT DISTINCT Milk.cart_id
FROM (SELECT * FROM CART_PRODUCTS WHERE NAME='Milk') Milk 
INNER JOIN (SELECT * FROM CART_PRODUCTS WHERE NAME='Yogurt') Yogurt
ON Milk.CART_ID = Yogurt.CART_ID;

-- INNER JOIN(2)
SELECT DISTINCT Milk.cart_id
FROM (SELECT * FROM CART_PRODUCTS WHERE NAME='Milk') AS Milk 
INNER JOIN (SELECT * FROM CART_PRODUCTS WHERE NAME='Yogurt') AS Yogurt
ON Milk.CART_ID = Yogurt.CART_ID;