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Display only the duplicate column names appearing atleast thrice in MySQL
Use HAVING COUNT() for this. Let us first create a table −
mysql> create table DemoTable1351 -> ( -> StudentId int NOT NULL AUTO_INCREMENT PRIMARY KEY, -> StudentName varchar(40) -> ); Query OK, 0 rows affected (1.08 sec)
Insert some records in the table using insert command −
mysql> insert into DemoTable1351(StudentName) values('Chris');
Query OK, 1 row affected (0.19 sec)
mysql> insert into DemoTable1351(StudentName) values('Bob');
Query OK, 1 row affected (0.11 sec)
mysql> insert into DemoTable1351(StudentName) values('Bob');
Query OK, 1 row affected (0.11 sec)
mysql> insert into DemoTable1351(StudentName) values('David');
Query OK, 1 row affected (0.11 sec)
mysql> insert into DemoTable1351(StudentName) values('Bob');
Query OK, 1 row affected (0.11 sec)
mysql> insert into DemoTable1351(StudentName) values('David');
Query OK, 1 row affected (0.09 sec)
mysql> insert into DemoTable1351(StudentName) values('Bob');
Query OK, 1 row affected (0.09 sec)
mysql> insert into DemoTable1351(StudentName) values('Mike');
Query OK, 1 row affected (0.68 sec)
mysql> insert into DemoTable1351(StudentName) values('David');
Query OK, 1 row affected (0.12 sec)Display all records from the table using select statement −
mysql> select * from DemoTable1351;
This will produce the following output −
+-----------+-------------+ | StudentId | StudentName | +-----------+-------------+ | 1 | Chris | | 2 | Bob | | 3 | Bob | | 4 | David | | 5 | Bob | | 6 | David | | 7 | Bob | | 8 | Mike | | 9 | David | +-----------+-------------+ 9 rows in set (0.00 sec)
Here is the query to display the duplicate column names appearing atleast thrice −
mysql> select * from DemoTable1351 -> group by StudentName -> having count(StudentName) >=3;
This will produce the following output −
+-----------+-------------+ | StudentId | StudentName | +-----------+-------------+ | 2 | Bob | | 4 | David | +-----------+-------------+ 2 rows in set (0.00 sec)
Updated on: 05-Nov-2019
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