Querying the existence of an exact set of many to many relationship with Eloquent?-CodePudding

I need to make a query to find a Model that has an exact set of a many-to-many relationship.

For example, I have a Blog post that has many Tags. The tags can belongs to many blog posts.

How could I retrieve all blogs posts that have the tag #1, #2 and #3 without any other tag, only these 3, in an efficient manner?

CodePudding user response：

First approach that comes to my mind is a ->whereHas() for each Tag you want to find, something like:

$tagIds = [1, 2, 3];

$query = Blog::where(function ($query) use ($tagIds) {
  foreach ($tagIds as $tagId) {
    $query->whereHas('tags', function ($subQuery) use ($tagId) {
      return $subQuery->where('tags.id', $tagId); 
    });
  }
})->has('tags', '=', count($tagIds));

// Additional Clauses/Filters/Etc.

$blogs = $query->get();

This will execute an additional query for the Tags supplied (based on ID), and filter your Blog records to only those that match all supplied Tags.