Support for loose coupled duplicated column names for aggregators

[rafallyczkowski]

• Laravel Version: 7.27.0
• PHP Version: 7.4.9
• Database Driver & Version: MariaDB 10.5.5 MySQL

Description:

For aggregate selects it's forbidden to have a duplicated column names.

[2020-09-01 18:59:47] local.ERROR: SQLSTATE[42S21]: Column already exists: 1060 Duplicate column name 'description' (SQL: ... at /var/www/html/laravel/vendor/laravel/framework/src/Illuminate/Database/Connection.php:671)

Steps To Reproduce:

Execute this query.

$count = DB::query()->fromSub(function ($query) {
   $query
       ->from('users')
       ->addSelect('email')
       ->addSelect('email')
       ->groupBy('email');
}, 'a')->count();

Motivation

When using a repositories design patter, we are having criteria that build a query based on the data in the specific criteria,
we don't check on this level agains existing columns. I believe array_unique could be executed on the columns just before sending a query. It does not affect any column select aliases.