Hi friend,

public interface HttpServletRequest
extends ServletRequest
Extends the ServletRequest interface to provide request information for HTTP servlets.
The servlet container creates an HttpServletRequest object and passes it as an argument
to the servlet's service methods (doGet, doPost, etc).


Remove duplicate record :

MySQL remove duplicate

To remove duplicate entries in the MySQL database we can follow one of these following approach:

First approach is that we have to write three manual steps to create
the new backup table with unique entries then we will remove the older table and at
last we will rename the backup table with the same name of the older table that we have deleted.
Here is the explanation with the query :

To explain use we have to create a table which consists duplicate entries :
Query

CREATE TABLE `users` (
`id` int(11) NOT NULL,
`username` varchar(50) default NULL,
`password` varchar(50) default NULL,
`email` varchar(50) default NULL
) ENGINE=InnoDB DEFAULT CHARSET=latin1;

/*Data for the table `users` */

insert into `users`(`id`,`username`,`password`,`email`)
values (1,'Ankur','ankur','ankur@yahoo.com'),
(2,'Sam','sam','sam@yahoo.com'),
(3,'Xavior','xavior','xav@yahoo.com'),
(1,'Suman','suman','suman@one.com');

select * from users;

Output

+----+----------+----------+-----------------+
| id | username | password | email |
+----+----------+----------+-----------------+
| 1 | Ankur | ankur | ankur@yahoo.com |
| 2 | Sam | sam | sam@yahoo.com |
| 3 | Xavior | xavior | xav@yahoo.com |
| 1 | Suman | suman | suman@one.com |
+----+----------+----------+-----------------+
4 rows in set (0.00 sec)

Now to remove duplicate entries we can execute following query:
Query

CREATE TABLE backup_table AS
SELECT * FROM users WHERE 1 GROUP BY id ;
DROP TABLE users;
RENAME TABLE backup_table TO users;

Output

+----+----------+----------+-----------------+
| id | username | password | email |
+----+----------+----------+-----------------+
| 1 | Ankur | ankur | ankur@yahoo.com |
| 2 | Sam | sam | sam@yahoo.com |
| 3 | Xavior | xavior | xav@yahoo.com |
+----+----------+----------+-----------------+

Second approach to remove duplicate entries from the database table is
very simple and is extremely quick way to remove duplicates. Here is the query :
Query

ALTER IGNORE TABLE users ADD UNIQUE INDEX(id);

Output

+----+----------+----------+-----------------+
| id | username | password | email |
+----+----------+----------+-----------------+
| 1 | Ankur | ankur | ankur@yahoo.com |
| 2 | Sam | sam | sam@yahoo.com |
| 3 | Xavior | xavior | xav@yahoo.com |
+----+----------+----------+-----------------+

In the above query we have added unique index for id.