MySQL query to count the duplicate ID values and display the result in a separate column
To count the duplicate ID values, use aggregate function COUNT() and GROUP BY. Let us first create a table −
mysql> create table DemoTable
(
Id int,
Name varchar(100)
);
Query OK, 0 rows affected (1.30 sec)
Insert some records in the table using insert command −
mysql> insert into DemoTable values(50,'Chris');
Query OK, 1 row affected (0.19 sec)
mysql> insert into DemoTable values(51,'David');
Query OK, 1 row affected (0.15 sec)
mysql> insert into DemoTable values(51,'Mike');
Query OK, 1 row affected (0.18 sec)
mysql> insert into DemoTable values(50,'Sam');
Query OK, 1 row affected (0.17 sec)
Display all records from the table using select statement −
mysql> select *from DemoTable;
This will produce the following output −
+------+-------+
| Id | Name |
+------+-------+
| 50 | Chris |
| 51 | David |
| 51 | Mike |
| 50 | Sam |
+------+-------+
4 rows in set (0.00 sec)
Following is the query to display the count of duplicate ID values in a new column −
mysql> select Id,count(Name) as Count
from DemoTable
group by Id;
This will produce the following output −
+------+-------+
| Id | Count |
+------+-------+
| 50 | 2 |
| 51 | 2 |
+------+-------+
2 rows in set (0.00 sec)
Published on 01-Oct-2019 11:17:13
