How to determine if there are duplicate values ​​in an array written to the database

Question

There are many identical arrays

name=user[],name=qian[],name=duo[].

name=user[],name=qian[] ,name=duo[]

name=user[],name=qian[],name=duo[]

1. How to obtain the backend?

2. How does the backend determine that the same value exists in the database and prompts for duplication.

Answer 1

Example