[걷기반] 9)아프면 안됩니다! 항상 건강 챙기세요!

의사가 있으면 당연히 의사에게 진료받는 환자가 있겠죠? 아래와 같은 patients(환자) 테이블이 있습니다.

id	name	birth_date	gender	last_visit_date
1	르탄이	1985-04-12	남자	2023-03-15
2	배캠이	1990-08-05	여자	2023-03-20
3	구구이	1982-12-02	여자	2023-02-18
4	이션이	1999-03-02	남자	2023-03-1

34. patients 테이블에서 각 성별(gender)에 따른 환자 수를 계산하는 쿼리를 작성해주세요!

select gender, count(*) as patients_count
from patients
group by gender;

 

35. patients 테이블에서 현재 나이가 40세 이상인 환자들의 수를 계산하는 쿼리를 작성해주세요!

select count(*) as patients_count
from patients
where TIMESTAMPDIFF(year, birth_date, curdate()) >= 40;

 

36. patients 테이블에서 마지막 방문 날짜(last_visit_date)가 1년 이상 된 환자들을 선택하는 쿼리를 작성해주세요!

select *
from patients
where timestampdiff(year, last_visit_date, curdate()) >= 1;

 

37. patients 테이블에서 생년월일이 1980년대인 환자들의 수를 계산하는 쿼리를 작성해주세요!

select count(*)
from patients
where year(birth_date) between 1980 and 1989;