Форум пользователей MySQL

mysql> create table temp (id int not null auto_increment primary key) engine=innodb;
Query OK, 0 rows affected (0.14 sec)

mysql> insert into temp values(null),(null);
Query OK, 2 rows affected (0.03 sec)
Records: 2  Duplicates: 0  Warnings: 0

mysql> select * from temp;
+----+
| id |
+----+
|  1 |
|  2 |
+----+
2 rows in set (0.00 sec)

mysql> insert into temp select null from temp;
Query OK, 2 rows affected (0.06 sec)
Records: 2  Duplicates: 0  Warnings: 0

mysql> select * from temp;
+----+
| id |
+----+
|  1 |
|  2 |
|  3 |
|  4 |
+----+
4 rows in set (0.00 sec)

mysql> insert into temp select null from temp;
Query OK, 4 rows affected (0.03 sec)
Records: 4  Duplicates: 0  Warnings: 0

mysql> select * from temp;
+----+
| id |
+----+
|  1 |
|  2 |
|  3 |
|  4 |
|  6 |
|  7 |
|  8 |
|  9 |
+----+
8 rows in set (0.02 sec)