Here is a pure SQL solution, which works only if the column being swapped is not a unique key.
mysql> select * from swaptable;
+----+------+
| id | num |
+----+------+
| 5 | 100 |
| 6 | 200 |
| 7 | 300 |
+----+------+
3 rows in set (0.00 sec)
mysql> UPDATE swaptable SET id = CASE id WHEN 5 THEN 6
-> WHEN 6 THEN 5 END
-> WHERE id IN (5,6);
Query OK, 2 rows affected (0.01 sec)
Rows matched: 2 Changed: 2 Warnings: 0
mysql> select * from swaptable;
+----+------+
| id | num |
+----+------+
| 6 | 100 |
| 5 | 200 |
| 7 | 300 |
+----+------+
3 rows in set (0.00 sec)
mysql> UPDATE swaptable SET id = CASE id WHEN 5 THEN 6
-> WHEN 6 THEN 5 END
-> WHERE id IN (5,6);
Query OK, 2 rows affected (0.01 sec)
Rows matched: 2 Changed: 2 Warnings: 0
mysql> select * from swaptable;
+----+------+
| id | num |
+----+------+
| 5 | 100 |
| 6 | 200 |
| 7 | 300 |
+----+------+
3 rows in set (0.00 sec)
