How not to add the same values ​​to the database + check one field?

Question

MySQL

Good afternoon!
There is a request:

insert into test1 (case_id, component_number, component_name, test_type, test_name, test_description, cft, bisquit, cif, cifle)
values ('1', '018', 'nam_comp', 'pos', 't_01', 'тут текст', '1', 'false', 'false', 'false')
ON CONFLICT (case_id) DO update set
test_description='--новый текст--';

Need advice on how to remake the table or rewrite the query so that:
1. when adding new records, the same records are not added
2. if the test_description in the new record has been changed, you need to change it in the old record

Answer 1

1. when adding new records, the same records were not added

Compare the new record, and find the old one by it. If there is no old one, then add it; if there is, then do not add it.
I didn’t quite understand what it was about, but if I understood it, then also check the test_description of the new record and the test_description of the old record. If the text is different, then replace the test_description of the old entry with the test_description of the new entry.
Something like this.

Answer 2

INSERT ... ON DUPLICATE KEY UPDATE for mysql