Selecting carefully with Laravel Joins

When joining two tables in Laravel, you have to be specific about what you're selecting.

Laravel joins

Let's say you have two tables, users and posts. Both have id columns, and posts has a user_id that is a foreign key to the users table.

To join the two tables together, you use the #join method

$user = User
  ::join('posts', 'posts.user_id', '=', 'users.id')
  ->first();

But the results you get may be surprising

print $user->id; //prints the id of the posts table

The Problem

The query generated by a join clause uses a select all by default, so you can accidentally override columns

SELECT * FROM users INNER JOIN posts ON posts.user_id = users.id

It results in two id columns returned, and internally the id attribute is set to the second column (from the posts table).

The solution

To work around this issue, make sure you are specific with your select clause

$user = User
  ::join('posts', 'posts.user_id', '=', 'users.id')
  ->select('users.*')
  ->first();

Now the results are what you would expect

print $user->id; //prints the id of the users table