You can use DELETE command with some condition for this since we need to keep one record and delete rest of the duplicate records.
Let us first create a table −
mysql> create table DemoTable ( StudentId int NOT NULL AUTO_INCREMENT PRIMARY KEY, StudentName varchar(40) ); Query OK, 0 rows affected (0.48 sec)
Insert records in the table using insert command −
mysql> insert into DemoTable(StudentName) values('John');
Query OK, 1 row affected (0.16 sec)
mysql> insert into DemoTable(StudentName) values('Carol');
Query OK, 1 row affected (0.17 sec)
mysql> insert into DemoTable(StudentName) values('Sam');
Query OK, 1 row affected (0.28 sec)
mysql> insert into DemoTable(StudentName) values('Carol');
Query OK, 1 row affected (0.14 sec)
mysql> insert into DemoTable(StudentName) values('David');
Query OK, 1 row affected (0.19 sec)
mysql> insert into DemoTable(StudentName) values('Carol');
Query OK, 1 row affected (0.26 sec)Display records from the table using select command −
mysql> select *from DemoTable;
This will produce the following output −
+-----------+-------------+ | StudentId | StudentName | +-----------+-------------+ | 1 | John | | 2 | Carol | | 3 | Sam | | 4 | Carol | | 5 | David | | 6 | Carol | +-----------+-------------+ 6 rows in set (0.00 sec)
Here is the query to remove duplicate records except a single record −
mysql> delete tbl1 from DemoTable tbl1,DemoTable tbl2 WHERE tbl1.StudentName = tbl2.StudentName AND tbl1.StudentId > tbl2.StudentId; Query OK, 2 rows affected (0.79 sec)
The above query deleted 2 rows for “Carol” and left one of the “Carol” record.
Let us now display the records of table −
mysql> select *from DemoTable;
This will produce the following output −
+-----------+-------------+ | StudentId | StudentName | +-----------+-------------+ | 1 | John | | 2 | Carol | | 3 | Sam | | 5 | David | +-----------+-------------+ 4 rows in set (0.00 sec)