mysql> create table DuplicateDeleteDemo
   -> (
   -> id int,
   -> name varchar(100)
   -> );
Query OK, 0 rows affected (0.60 sec)

mysql> insert into DuplicateDeleteDemo values(1,'John');
Query OK, 1 row affected (0.11 sec)

mysql>  insert into DuplicateDeleteDemo values(1,'John');
Query OK, 1 row affected (0.14 sec)

mysql>  insert into DuplicateDeleteDemo values(2,'Johnson');
Query OK, 1 row affected (0.13 sec)

mysql>  insert into DuplicateDeleteDemo values(1,'John');
Query OK, 1 row affected (0.14 sec)

mysql> select *from DuplicateDeleteDemo;

+------+---------+
| id   | name    |
+------+---------+
|    1 | John    |
|    1 | John    |
|    2 | Johnson |
|    1 | John    |
+------+---------+
4 rows in set (0.00 sec)

mysql> delete from DuplicateDeleteDemo where id=1;
Query OK, 3 rows affected (0.19 sec)

mysql> select *from DuplicateDeleteDemo;

+------+---------+
| id   | name    |
+------+---------+
|    2 | Johnson |
+------+---------+
1 row in set (0.00 sec)