如何使用mysql对基于基本整数的varchar id进行排序

Question

Testcase_id in my system are varchar and generated by trigger and I want to sort them on basis of the integer value of the varchar id . I have been so far used three queries but not working at all. I have also tried with the function which converts string to integer. Here I am mentioning that function also and my query well in this query i have not used function.

select t.Testcase_id, 
       CONVERT(SUBSTRING_INDEX('t.Testcase_id','_',2),UNSIGNED INTEGER) as num 
from testcase_master t 
order by num

output(of query):

Answer 1

You have to use -1 instead of 2 inside SUBSTRING_INDEX :

select t.Testcase_id,      
       CONVERT(SUBSTRING_INDEX(t.Testcase_id,'_', -1),UNSIGNED INTEGER) as num 
from testcase_master t 
order by num

According to the manual :

Returns the substring from string str before count occurrences of the delimiter delim. If count is positive , everything to the left of the final delimiter (counting from the left ) is returned. If count is negative , everything to the right of the final delimiter (counting from the right ) is returned.

Demo here

Answer 2

use Cast

CAST(col AS UNSIGNED)

or REPLACE with CAST

CAST(REPLACE(testcase_id,'TC_CTU_','') AS UNSIGNED)

Your query :-

select t.Testcase_id, 
       CAST(REPLACE(testcase_id,'TC_CTU_','') AS UNSIGNED) as num 
from testcase_master t 
order by num