Implement numbering in MySQL GROUP_CONCAT


Let us first create a table −

mysql> create table DemoTable1627
    -> (
    -> FirstName varchar(20),
    -> LastName varchar(20)
    -> );
Query OK, 0 rows affected (0.59 sec)

Insert some records in the table using insert command.

mysql> insert into DemoTable1627 values('John','Smith');
Query OK, 1 row affected (0.11 sec)
mysql> insert into DemoTable1627 values('John','Doe');
Query OK, 1 row affected (0.13 sec)
mysql> insert into DemoTable1627 values('Adam','Smith');
Query OK, 1 row affected (0.18 sec)
mysql> insert into DemoTable1627 values('Carol','Taylor');
Query OK, 1 row affected (0.08 sec)

Display all records from the table using select statement −

mysql> select * from DemoTable1627;

This will produce the following output −

+-----------+----------+
| FirstName | LastName |
+-----------+----------+
| John      | Smith    |
| John      | Doe      |
| Adam      | Smith    |
| Carol     | Taylor   |
+-----------+----------+
4 rows in set (0.00 sec)

Here is the query to implement group_concat() numbering −

mysql> select  LastName,
    -> group_concat(
    -> concat(@j := if (@p = LastName, @j + 1, if(@p := LastName,1,1)), '.', FirstName)
    -> separator ', ') FirstName
    -> from   DemoTable1627
    -> group by LastName;

This will produce the following output −

+----------+----------------+
| LastName | FirstName      |
+----------+----------------+
| Doe      | 1.John       |
| Smith    | 1.John, 2.Adam |
| Taylor   | 1.Carol       |
+----------+----------------+
3 rows in set (0.09 sec)
raja
Published on 08-Nov-2019 11:19:16
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