LeetCode MySQL 626. 换座位

示例：
+---------+---------+
|    id   | student |
+---------+---------+
|    1    | Abbot   |
|    2    | Doris   |
|    3    | Emerson |
|    4    | Green   |
|    5    | Jeames  |
+---------+---------+
假如数据输入的是上表，则输出结果如下：
+---------+---------+
|    id   | student |
+---------+---------+
|    1    | Doris   |
|    2    | Abbot   |
|    3    | Green   |
|    4    | Emerson |
|    5    | Jeames  |
+---------+---------+
注意：
如果学生人数是奇数，则不需要改变最后一个同学的座位。

# Write your MySQL query statement below
select id1 as id, student
from
(
    select case when id%2=1 and id+1 <= (select count(*) from seat)
                        then id+1
                when id%2=0 then id-1
                else id end as id1,
           student
    from seat
) t
order by id1