MySQL query to replace special characters from column value

Let us first create a table −

mysql> create table DemoTable1574
   -> (
   -> StudentCode varchar(20)
   -> );
Query OK, 0 rows affected (0.59 sec)

Insert some records in the table using insert command −

mysql> insert into DemoTable1574 values('111_Carol');
Query OK, 1 row affected (0.14 sec)
mysql> insert into DemoTable1574 values('______');
Query OK, 1 row affected (0.30 sec)
mysql> insert into DemoTable1574 values('David_12345');
Query OK, 1 row affected (0.14 sec)
mysql> insert into DemoTable1574 values('______');
Query OK, 1 row affected (0.12 sec)

Display all records from the table using select statement −

mysql> select * from DemoTable1574;

This will produce the following output −

+-------------+
| StudentCode |
+-------------+
| 111_Carol   |
| ______      |
| David_12345 |
| ______      |
+-------------+
4 rows in set (0.00 sec)

Here is the query to replace −

mysql> update DemoTable1574 set StudentCode=replace(StudentCode,'______','Mike_007');
Query OK, 2 rows affected (0.38 sec)
Rows matched: 4  Changed: 2 Warnings: 0

Let us check the table records once again −

mysql> select * from DemoTable1574;

This will produce the following output −

+-------------+
| StudentCode |
+-------------+
| 111_Carol   |
| Mike_007    |
| David_12345 |
| Mike_007    |
+-------------+
4 rows in set (0.00 sec)