Laravel Eloquent, select only rows where the relation exists

问题

I am trying to select from a table, but I only want to select things that have an existing relationship.

For example, if I have Users and Comments, and Users haveMany Comments, I want to do something like:

User::hasComments()->paginate(20);

So, I only want to select Users that have at least 1 Comment, and paginate the result of that query. Is there any way to do this?

回答1:

According to Laravel's Eloquent documentation for querying relations (look for the "Querying Relationship Existence" subheading), this should work:

User::has('comments')->paginate(20);

回答2:

Flip your thinking upside down and I think that you can do it.

$userIds = Comment::distinct()->select('user_id')->groupBy('user_id')->get();

You may not need the groupBy() but that should get you started towards a way to do it.

Then you should be able to iterate through each like so:

foreach($userIds as $id) {
    $user = $id->user;  //$id is technically a Comment instance so you can
                        //  call the methods on that model
    echo $user->name;
}

来源：https://stackoverflow.com/questions/31598949/laravel-eloquent-select-only-rows-where-the-relation-exists