交换座位

 

换座位 - LeetCode (中国) https://leetcode-cn.com/problems/exchange-seats/description/

 

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  |
+---------+---------+ 

SELECT * FROM (
SELECT a.id,b.student FROM seat a LEFT JOIN seat b ON a.id=b.id-1 WHERE a.id MOD 2=1 AND a.id!=(SELECT MAX(id) FROM seat)
UNION ALL
SELECT * FROM seat WHERE id MOD 2=1 AND id=(SELECT MAX(id) FROM seat)
UNION ALL
SELECT a.id,b.student FROM seat a LEFT JOIN seat b ON a.id=b.id+1 WHERE a.id MOD 2=0
) AS t
ORDER BY id ASC;