[Programmers] IFNULL, 조건에 맞는 값 구하기

* NULL 일때 처리

SELECT WAREHOUSE_ID, WAREHOUSE_NAME, ADDRESS, IFNULL(FREEZER_YN, 'N') AS FREEZER_YN
FROM FOOD_WAREHOUSE
WHERE ADDRESS LIKE '%경기도%'
ORDER BY WAREHOUSE_ID;

만약 FREEZER_YN이 NULL 일때 'N'으로 처리

SELECT 절에서 IFNULL(FREEZER_YN, 'N') AS FREEZER_YN

 

* 조건에 맞는 값 구하기

SELECT COUNT(*) AS USERS
FROM USER_INFO
WHERE AGE >= 20 AND AGE <=29 AND YEAR(JOINED) = 2021 ;

SELECT COUNT(*) AS USERS
FROM USER_INFO
WHERE AGE BETWEEN 20 AND 29 AND YEAR(JOINED) = 2021;