mysqlで主キーを削除するにはどうすればよいですか?

ALTER  TABLE  TABLE_NAME  DROP  PRIMARY  KEY;

mysql> create table test1_3(
    -> id int not null primary key,
    -> name char(10)
    -> );
Query OK, 0 rows affected (0.01 sec)

mysql> alter table test1_3 drop primary key;
Query OK, 0 rows affected (0.02 sec)
Records: 0  Duplicates: 0  Warnings: 0

mysql> create table test1_2(
    -> id int not null  auto_increment,
    -> name char(10),-> primary key(id)
    -> );
Query OK, 0 rows affected (0.00 sec)

mysql> desc test1_2;
+-------+----------+------+-----+---------+----------------+
| Field | Type     | Null | Key | Default | Extra          |
+-------+----------+------+-----+---------+----------------+
| id    | int(11)  | NO   | PRI | NULL    | auto_increment |
| name  | char(10) | YES  |     | NULL    |                |
+-------+----------+------+-----+---------+----------------+
2 rows in set (0.00 sec)

mysql> alter table test1_2 drop primary key;

ERROR 1075 (42000): Incorrect table definition; there can be only one auto column and it must be defined as a key               
#这说明此列是自动增长列，无法直接删除