[나이 정보가 없는 회원 수 구하기]
조건걸때 IS NULL
SELECT
COUNT(*) AS USERS
FROM USER_INFO
WHERE AGE IS NULL
[경기도에 위치한 식품창고 목록 출력하기]
SELECT
WAREHOUSE_ID
,WAREHOUSE_NAME
,ADDRESS
,COALESCE(FREEZER_YN,'N') AS FREEZER_YN
FROM FOOD_WAREHOUSE
WHERE WAREHOUSE_NAME LIKE '%경기%'
ORDER BY WAREHOUSE_ID ASC
# NULL 값 처리
1) CASE WHEN TLNO IS NULL THEN 'NONE'ELSE TLNO END
2) ISNULL(TLNO, 'NONE') -> SQL Server
3) COALESCE( (TLNO, 'NONE')
4) IFNULL(TLNO , 'N')
5) IF(TLNO IS NULL, 'N' , TLNO)
=> 만약 TLNO가 NULL이면 'N'로 바꿔줘!