phpmyadmin - mysql searches the index and finds the key_name of id_2. What index is this? ?

Question

mysql searches the index and finds the key_name of id_2. What index is this? ?
SHOW INDEX FROM spm_works, the result is as shown below:

Answer 1

You should be the ordinary index you created. Show the creation statement of the spm_works table: show create table spm_works; See if the id_2 index line is created.

Answer 2

id_2 This is the name of the index built on the id field. Obviously this is a normal index and is not unique.