[리트코드] 626. Exchange Seats - 해결한문제, lag, lead

 

# 문제

https://leetcode.com/problems/exchange-seats/

 

# 문제 요약

 

(1,2) / (3,4) ... 번째 순서끼리 바꾸고 마지막 id값이 홀수라면 바꾸지 않는다

 

 

# 문제 해결

 

lag(컬럼,1) over (order by 컬럼) as 별칭

1행 위에 있는 컬럼값을 가져온다

 

lead(컬럼,1) over (order by 컬럼) as 별칭

1행 밑에 있는 컬럼값을 가져온다

 

 

# 정답코드

 

with cte as (
    select *,
       lag(student,1) over (order by id) as lag_text,
       lead(student,1) over (order by id) as lead_text
    from Seat
)
select id,
       case when id % 2 = 1 and id = (select count(*) from cte) then student
            when id % 2 = 1 then lead_text
            when id % 2 = 0 then lag_text
            end as student
from cte