GROUP BY the number of rows returned by GROUP BY in MySQL?
You can use GROUP_CONCAT() for this. To understand the above concept, let us create a table.
The query to create a table is as follows
mysql> create table groupByDemo
-> (
-> Id int NOT NULL AUTO_INCREMENT PRIMARY KEY,
-> Name varchar(100)
-> );
Query OK, 0 rows affected (1.31 sec)
Insert some records in the table using insert command.
The query is as follows
mysql> insert into groupByDemo(Name) values('John');
Query OK, 1 row affected (0.19 sec)
mysql> insert into groupByDemo(Name) values('Carol');
Query OK, 1 row affected (0.14 sec)
mysql> insert into groupByDemo(Name) values('Carol');
Query OK, 1 row affected (0.10 sec)
mysql> insert into groupByDemo(Name) values('Bob');
Query OK, 1 row affected (0.24 sec)
mysql> insert into groupByDemo(Name) values('Bob');
Query OK, 1 row affected (0.23 sec)
mysql> insert into groupByDemo(Name) values('Bob');
Query OK, 1 row affected (0.17 sec)
mysql> insert into groupByDemo(Name) values('John');
Query OK, 1 row affected (0.16 sec)
mysql> insert into groupByDemo(Name) values('John');
Query OK, 1 row affected (0.07 sec)
mysql> insert into groupByDemo(Name) values('John');
Query OK, 1 row affected (0.11 sec)
mysql> insert into groupByDemo(Name) values('Sam');
Query OK, 1 row affected (0.17 sec)
mysql> insert into groupByDemo(Name) values('Carol');
Query OK, 1 row affected (0.19 sec)Display all records from the table using select statement.
The query is as follows
mysql> select *from groupByDemo;
The following is the output
+----+-------+
| Id | Name |
+----+-------+
| 1 | John |
| 2 | Carol |
| 3 | Carol |
| 4 | Bob |
| 5 | Bob |
| 6 | Bob |
| 7 | John |
| 8 | John |
| 9 | John |
| 10 | Sam |
| 11 | Carol |
+----+-------+
11 rows in set (0.00 sec)
Here is the query to group by number of rows
mysql> SELECT Counter, GROUP_CONCAT(Name SEPARATOR ', ') as AllName
-> FROM (SELECT Name, COUNT(Name) as Counter
-> FROM groupByDemo
-> GROUP BY Name) tbl
-> GROUP BY Counter
-> ORDER BY Counter DESC;
The following is the output
+---------+------------+
| Counter | AllName |
+---------+------------+
| 4 | John |
| 3 | Carol, Bob |
| 1 | Sam |
+---------+------------+
3 rows in set (0.00 sec)
Published on 29-Mar-2019 11:26:53
