SQL finding mismatches within the same column

SQL Noob here.
I’m struggling with a (hopefully) simple SQL query and would appreciate if someone could help me understand if what I’m trying to do is even possible. I already completed the task outside SQL so this is just my curiosity.

Task is simple.
I have a Table with millions of Codes. There are 12 digit codes always starting with ‘00000’ and their 7 digit equivalents. (like 000001234567 and 1234567)
I’d need to identify all 12 digit codes that DO NOT have equivalent 7 digit code within the same column.

Any help appreciated.

This is the data of the table :

and the expected output is :

>Solution :

You can use TRIM() function and HAVING clause along with GROUP BY such as

 SELECT CONCAT('00000',TRIM(LEADING '0' FROM code))
   FROM t
  GROUP BY CONCAT('00000',TRIM(LEADING '0' FROM code)) 
  HAVING COUNT(TRIM(LEADING '0' FROM code))=1 

Demo