这是leetcode的交换席位问题。
老师想给相邻的学生换座位。输入：

+---------+---------+
|    id   | student |
+---------+---------+
|    1    | Abbot   |
|    2    | Doris   |
|    3    | Emerson |
|    4    | Green   |
|    5    | Jeames  |
+---------+---------+

输出：

+---------+---------+
|    id   | student |
+---------+---------+
|    1    | Doris   |
|    2    | Abbot   |
|    3    | Green   |
|    4    | Emerson |
|    5    | Jeames  |
+---------+---------+

给定解决方案：

SELECT
    (CASE
        WHEN MOD(id, 2) != 0 AND counts != id THEN id + 1
        WHEN MOD(id, 2) != 0 AND counts = id THEN id
        ELSE id - 1
    END) AS id,
    student
FROM
    seat,
    (SELECT
        COUNT(*) AS counts
    FROM
        seat) AS seat_counts
 ORDER BY id ASC;

我的解决方案：

select 
(Case 
    when mod(id,2) !=0 and id != count(*) then id + 1
    when mod(id,2) !=0 and id = count(*) then id
    else id - 1
 end) as 'id',
 student
from seat
order by id;

给定的解决方案效果很好，但我的只能得到一行输出。
我的输出：

+---------+---------+
|    id   | student |
+---------+---------+
|    2    | Abbot   |
+---------+---------+

有人能解释一下我的解决方案和给定的解决方案有什么区别，为什么我的解决方案是错误的吗？谢谢。