Algorithm
Problem Name: 626. Exchange Seats
Problem Link: https://leetcode.com/problems/exchange-seats/
SQL Schema
Table: Seat
+-------------+---------+ | Column Name | Type | +-------------+---------+ | id | int | | student | varchar | +-------------+---------+ id is the primary key column for this table. Each row of this table indicates the name and the ID of a student. id is a continuous increment.
Write an SQL query to swap the seat id of every two consecutive students. If the number of students is odd, the id of the last student is not swapped.
Return the result table ordered by id in ascending order.
The query result format is in the following example.
Example 1:
Input: Seat table: +----+---------+ | id | student | +----+---------+ | 1 | Abbot | | 2 | Doris | | 3 | Emerson | | 4 | Green | | 5 | Jeames | +----+---------+ Output: +----+---------+ | id | student | +----+---------+ | 1 | Doris | | 2 | Abbot | | 3 | Green | | 4 | Emerson | | 5 | Jeames | +----+---------+ Explanation: Note that if the number of students is odd, there is no need to change the last one's seat.
Code Examples
#1 Code Example with SQL
Code -
SQL
SELECT
s1.id, COALESCE(s2.student, s1.student) AS student
FROM
seat s1
LEFT JOIN
seat s2 ON ((s1.id + 1) ^ 1) - 1 = s2.id
ORDER BY s1.id;
Input
Seat table:
+----+---------+
| id | student |
+----+---------+
| 1 | Abbot |
| 2 | Doris |
| 3 | Emerson |
| 4 | Green |
| 5 | Jeames |
+----+---------+
Output
+----+---------+
| id | student |
+----+---------+
| 1 | Doris |
| 2 | Abbot |
| 3 | Green |
| 4 | Emerson |
| 5 | Jeames |
+----+---------+