MYSQL A question about using character functions to filter data

Problem description:

structure:

test has two fields,
They are col1 and col2, both are character fields.
The contents are three numbers separated by , and they correspond one to one.

For example, col1 content is: 26,59,6
col2 content is: 1502.5,1690,2276.77
The one-to-one correspondence is that the value of 26 is 1502.5, 59 is 1690, and 6 corresponds to 2276.77

Search criteria:

Select an id, such as 59, and then enter a number, such as: 2000
Then we search for records with id=59 in col1, and then search for records with col2 less than 2000, that is, 1690<2000

Example:

If there are the following three records, search for records with id 59 and value less than 2000:

26,59,6 | 1502.5,1690,2276.77
59,33,6 | 3502.1,1020,2276.77
22,8,59 | 1332.6,2900,1520.77

The three records with id 59 are searched, and then the second search condition is determined to be (that is, the numbers at the corresponding id positions are compared):

1690<2000
3502.1>2000
1520.77<2000

drop table test; 
create table test ( col1 varchar(100), col2 varchar(100)); 
insert test select 
'26,59,6', '1502.5,1690,2276.77' union all select 
'59,33,6', '3502.1,1020,2276.77' union all select 
'22,8,59', '1332.6,2900,1520.77'; 
select col1,col2 
from (select *,find_in_set('59',col1) as rn from test) k 
where substring_index(concat(',',substring_index(col2,',',rn)),',',-1) 
 <'2000'; 

+---------+---------------------+

| col1 | col2 |

+---------+---------------------+

| 26,59,6 | 1502.5,1690,2276.77 |

| 22,8,59 | 1332.6,2900,1520.77 |

+---------+---------------------+