How to use comparison operator for numeric string in MySQL?

To use comparison operator for numeric string, use the substring() method. Let us first create a table −

mysql> create table DemoTable1881
   (
   UserId int,
   UserEducationGap varchar(20)
   );
Query OK, 0 rows affected (0.00 sec)

Insert some records in the table using insert command −

mysql> insert into DemoTable1881 values(101,'5-9');
Query OK, 1 row affected (0.00 sec)
mysql> insert into DemoTable1881 values(102,'2-4');
Query OK, 1 row affected (0.00 sec)
mysql> insert into DemoTable1881 values(103,'4-8');
Query OK, 1 row affected (0.00 sec)
mysql> insert into DemoTable1881 values(104,'7-12');
Query OK, 1 row affected (0.00 sec)

Display all records from the table using select statement −

mysql> select * from DemoTable1881;

This will produce the following output −

+--------+------------------+
| UserId | UserEducationGap |
+--------+------------------+
|    101 | 5-9              |
|    102 | 2-4              |
|    103 | 4-8              |
|    104 | 7-12             |
+--------+------------------+
4 rows in set (0.00 sec)

Here is the query to use comparison operator for numeric string in MySQL 

mysql> select * from DemoTable1881 where
cast(substring(UserEducationGap, 1, instr(UserEducationGap, '-')-1) as signed) >= 4;

This will produce the following output −

+--------+------------------+
| UserId | UserEducationGap |
+--------+------------------+
|    101 | 5-9              |
|    103 | 4-8              |
|    104 | 7-12             |
+--------+------------------+
3 rows in set (0.00 sec)