How to get "unique" users by combining email and date - mysql

Question

I am using Laravel 5.5.
I have a database which contains users. The problem is that some users exist more than one time because of a bug. I want to query my database and select all "unique" users.
By using the word "unique" I mean the below :
If a user with email "test#test.com" exists 50 times I want the row that created_at is closest to now.
My query, which returns all users is written below :
DB::table('users')
->select('name', 'surname', 'email', 'phone', 'answers', 'newsletter', 'created_at')
->get();
I got confused and I'm not sure if i should use limit combining it with order by created_at column.
Any ideas?

Answer 1

Ok, this is what you need to do: First off, you get a table with the users in their last created_at 'version'. Now you have a list of emails and dates. Then you perform a left join of all the users with that temporary table.
TL;DR:
$users = DB::select('select t1.* from users t1 right join (SELECT email, MAX(created_at) as created_at from users group by email) as t2 on t1.email=t2.email and t1.created_at=t2.created_at');
I hate raw SQL, and I hate subqueries, but this is the only way I know using generic SQL (I mean, you could do a better MySQL or MSSQL native queries, but this should do for you.)

Answer 2

You can use
DB::table('users')->select('name', 'surname', 'email','phone','answers','newsletter','created_at')->orderBy('created_at', 'desc')->groupBy('email')->get();
For more help refer Order By before Group By using Eloquent (Laravel)

Answer 3

What you need is groupby and orderby
try this code
DB::table('users')->select('name', 'surname', 'email','phone','answers','newsletter','created_at')
->orderBy('created_at', 'desc')
->groupBy('email')
->get();
hope it will help you if you need further info try above link!

Answer 4

To get latest user record among duplicates you can use a self join
DB::table('users as u')
->select('u.*')
->leftJoin('users as u1', function ($join) {
$join->on('u.email', '=', 'u1.email')
->whereRaw(DB::raw('u.created_at < u1.created_at'));
})
->whereNull('u1.id')
->get();
In plain SQL it would be something like
select u.*
from users u
left join users u1 on u.email = u1.email
and u.created_at < u1.created_at
where u1.id is null