[걷기반] 6) 팀 프로젝트 열심히 했으니 다시 놀아볼까요?!

create table lol_users (
	id int not null auto_increment,
    name varchar(20) not null,
    region varchar(20) not null,
    rating int not null,
    join_date datetime,
    constraint lol_users_PK primary key(id)
);

insert into lol_users (name, region, rating, join_date) values ("르탄이", "한국", 1300, "2019-06-15");
insert into lol_users (name, region, rating, join_date) values ("배캠이", "미국", 1500, "2020-09-01");
insert into lol_users (name, region, rating, join_date) values ("구구이", "한국", 1400, "2021-01-07");
insert into lol_users (name, region, rating, join_date) values ("이션이", "미국", 1350, "2019-11-15");

 

아래와 같은 lol_users(LOL 유저 테이블)이 있습니다

id	name	region	rating	join_date
1	르탄이	한국	1300	2019-06-15
2	배캠이	미국	1500	2020-09-01
3	구구이	한국	1400	2021-01-07
4	이션이	미국	1350	2019-11-15

 

21. lol_users 테이블에서 각 유저의 레이팅(rating) 순위를 계산하는 쿼리를 작성해주세요! 전체 지역(region) 기준이고 순위는 레이팅이 높을수록 높아야해요. (e.g. rating 1400 유저의 순위 > rating 1350 유저의 순위)

select name, rating, rank() over (order by rating desc) as ranking
from lol_users;

 

22. lol_users 테이블에서 가장 늦게 게임을 시작한(join_date) 유저의 이름을 선택하는 쿼리를 작성해주세요!

select name, join_date
from lol_users
order by join_date desc
limit 1;

 

23. lol_users 테이블에서 지역별로 레이팅이 높은 순으로 유저들을 정렬해서 나열하는 쿼리를 작성해주세요!

select *
from lol_users
order by region, rating desc;

 

24. lol_users 테이블에서 지역별로 평균 레이팅을 계산하는 쿼리를 작성해주세요!

select region, avg(rating) as average_rating
from lol_users
group by region;

 

 

 

[내일배움캠프-사전캠프 03일차] MySQL 랭킹(Ranking) 함수들