#1062 - Duplicate record '2-6' for key 'PRIMARY', how to fix?

Question

MySQL

I'm studying Symfony, and I came across such a problem, the Tag system does not want to work, an error in Mysql, when you add via the Admin panel (EasyAdmin) does not work, if you add it manually via phpMyAdmin, error 1062 crashes, but what's most interesting is the data to be added.

Table structure

Answer 1

You made the mistake yourself.
You want to add an entry with post_id=6, tag_id=2, while such an entry already exists in the database.
And it’s still not clear why in the database you have indexes for each column in addition to the composite PrimaryKey. In this case, they are redundant.