How to TRIM x number of characters, beginning from the last in MySQL?

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

mysql> create table DemoTable1329
   -> (
   -> StudentName varchar(40)
   -> );
Query OK, 0 rows affected (0.52 sec)

Insert some records in the table using insert command −

mysql> insert into DemoTable1329 values('David Miller');
Query OK, 1 row affected (0.16 sec)
mysql> insert into DemoTable1329 values('Chris Brown');
Query OK, 1 row affected (0.15 sec)
mysql> insert into DemoTable1329 values('Adam Smith');
Query OK, 1 row affected (0.24 sec)
mysql> insert into DemoTable1329 values('John Doe');
Query OK, 1 row affected (0.44 sec)

Display all records from the table using select statement −

mysql> select * from DemoTable1329;

This will produce the following output −

+--------------+
| StudentName  |
+--------------+
| David Miller |
| Chris Brown  |
| Adam Smith   |
| John Doe     |
+--------------+
4 rows in set (0.00 sec)

Here is the query to trim the X number of characters, beginning from the last −

mysql> select substring(StudentName, 1, length(StudentName) - 5) from DemoTable1329;

This will produce the following output −

+----------------------------------------------------+
| substring(StudentName, 1, length(StudentName) - 5) |
+----------------------------------------------------+
| David M                                            |
| Chris                                              |
| Adam                                               |
| Joh                                                |
+----------------------------------------------------+
4 rows in set (0.00 sec)