Check if the column values are the same among multiple records and set these records in a single row separated by a special character in MySQL

For this, you can use GROUP_CONCAT() along with DISTINCT. Let us first create a table −

mysql> create table DemoTable
(
   Id int,
   Subject varchar(40)
);
Query OK, 0 rows affected (0.56 sec)

Insert some records in the table using insert command −

mysql> insert into DemoTable values(100,'MySQL');
Query OK, 1 row affected (0.19 sec)
mysql> insert into DemoTable values(100,'MongoDB');
Query OK, 1 row affected (0.20 sec)
mysql> insert into DemoTable values(100,'Java');
Query OK, 1 row affected (0.14 sec)
mysql> insert into DemoTable values(100,'MongoDB');
Query OK, 1 row affected (0.11 sec)
mysql> insert into DemoTable values(101,'MySQL');
Query OK, 1 row affected (0.16 sec)
mysql> insert into DemoTable values(101,'MySQL');
Query OK, 1 row affected (0.10 sec)

Display all records from the table using select statement −

mysql> select *from DemoTable;

This will produce the following output −

+------+---------+
| Id   | Subject |
+------+---------+
| 100  | MySQL   |
| 100  | MongoDB |
| 100  | Java    |
| 100  | MongoDB |
| 101  | MySQL   |
| 101  | MySQL   |
+------+---------+
6 rows in set (0.00 sec)

Following is the query to check if the column values are the same among multiple records and set these records in a single row separated by a special character. The separator here is hyphen −

mysql> select Id,group_concat(distinct Subject separator '-') as Subject
   from DemoTable
   group by Id;

This will produce the following output −

+------+--------------------+
| Id   | Subject            |
+------+--------------------+
| 100  | Java-MongoDB-MySQL |
| 101  | MySQL              |
+------+--------------------+
2 rows in set (0.04 sec)