Exchange seats

LeetCode_626_Exchange Seats.sql

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+Create table If Not Exists seat(id int, student varchar(255))
+Truncate table seat
+insert into seat (id, student) values ('1', 'Abbot')
+insert into seat (id, student) values ('2', 'Doris')
+insert into seat (id, student) values ('3', 'Emerson')
+insert into seat (id, student) values ('4', 'Green')
+insert into seat (id, student) values ('5', 'Jeames')
+
+
+-- Mary is a teacher in a middle school and she has a table seat storing students' names and their corresponding seat ids.
+
+-- The column id is continuous increment.
+
+-- Mary wants to change seats for the adjacent students.
+
+-- Can you write a SQL query to output the result for Mary?
+
+
+
+-- +---------+---------+
+-- |    id   | student |
+-- +---------+---------+
+-- |    1    | Abbot   |
+-- |    2    | Doris   |
+-- |    3    | Emerson |
+-- |    4    | Green   |
+-- |    5    | Jeames  |
+-- +---------+---------+
+-- For the sample input, the output is:
+
+-- +---------+---------+
+-- |    id   | student |
+-- +---------+---------+
+-- |    1    | Doris   |
+-- |    2    | Abbot   |
+-- |    3    | Green   |
+-- |    4    | Emerson |
+-- |    5    | Jeames  |
+-- +---------+---------+
+-- Note:
+
+-- If the number of students is odd, there is no need to change the last one's seat.
+
+/* Write your T-SQL query statement below */
+
+
+select id, case 
+        when id%2=0 then (select student from seat where id =i.id-1)
+        when id%2!=0 and id < (select count(*) from seat) then (select student from seat where id=i.id+1)
+        else student
+        end as student
+        from seat i
+