How to match underscore in a MySQL String?

To match underscore in a MySQL string, you can use the below syntax −

select *from yourTableName where yourColumnName LIKE '%\_%';

Let us first create a table −

mysql> create table DemoTable
(
   ClientId varchar(200)
);
Query OK, 0 rows affected (0.79 sec)

Insert some records in the table using insert command −

mysql> insert into DemoTable values('CLI_101');
Query OK, 1 row affected (0.13 sec)
mysql> insert into DemoTable values('CLI1110');
Query OK, 1 row affected (0.13 sec)
mysql> insert into DemoTable values('_CLI102');
Query OK, 1 row affected (0.16 sec)
mysql> insert into DemoTable values('CLI103_');
Query OK, 1 row affected (0.12 sec)
mysql> insert into DemoTable values('CLI1111');
Query OK, 1 row affected (0.16 sec)

Following is the query to display all records from the table using select statement −

mysql> select *from DemoTable;

This will produce the following output −

+----------+
| ClientId |
+----------+
| CLI_101  |
| CLI1110  |
| _CLI102  |
| CLI103_  |
| CLI1111  |
+----------+
5 rows in set (0.00 sec)

Here is the query to match underscore in String using LIKE −

mysql> select *from DemoTable where ClientId LIKE '%\_%';

This will produce the following output displaying the strings with underscore −

+----------+
| ClientId |
+----------+
| CLI_101  |
| _CLI102  |
| CLI103_  |
+----------+
3 rows in set (0.00 sec)

You can use alternate query −

mysql> select *from DemoTable where ClientId REGEXP '_';

This will produce the following output −

+----------+
| ClientId |
+----------+
| CLI_101  |
| _CLI102  |
| CLI103_  |
+----------+
3 rows in set (0.00 sec)