Laravel - Union + Paginate at the same time?

Question

Brief:

I am trying to union 2 tables recipes and posts then add ->paginate(5) to the queries.

But for some reason I get this error:

Cardinality violation: 1222 The used SELECT statements have a different number of columns (SQL: (select count(*) as aggregate from posts

Code:

$recipes = DB::table("recipes")->select("id", "title", "user_id", "description", "created_at")
                    ->where("user_id", "=", $id);

$items = DB::table("posts")->select("id", "title", "user_id", "content", "created_at")
                ->where("user_id", "=", $id)
                ->union($recipes)
                ->paginate(5)->get();

Am i doing something wrong?

Without ->paginate(5) the query works fine.

Answer 1

You're right, pagination cause problem. Right now, you can create a view and query the view instead of the actual tables, or create your Paginator manually:

$page = Input::get('page', 1);
$paginate = 5;

$recipes = DB::table("recipes")->select("id", "title", "user_id", "description", "created_at")
            ->where("user_id", "=", $id);
$items = DB::table("posts")->select("id", "title", "user_id", "content", "created_at")
            ->where("user_id", "=", $id)
            ->union($recipes)
            ->get();

$slice = array_slice($items->toArray(), $paginate * ($page - 1), $paginate);
$result = Paginator::make($slice, count($items), $paginate);

return View::make('yourView',compact('result'));

Answer 2

I faced this kind of issue already. I found a thread also not about pagination but about unions.

Please see this link : Sorting UNION queries with Laravel 4.1

@Mohamed Azher has shared a nice trick and it works on my issue.

$query = $query1->union($query2);
$querySql = $query->toSql();
$query = DB::table(DB::raw("($querySql order by foo desc) as a"))->mergeBindings($query);

This creates an sql like below:

select * from (
  (select a as foo from foo)
  union
  (select b as foo from bar)
) as a order by foo desc;

And you can already utilize Laravel's paginate same as usual like $query->paginate(5). (but you have to fork it a bit to fit to your problem)

Answer 3

Reiterating jdme's answer with a more elegant method from Illuminate\Database\Query\Builder.

$recipes = DB::table("recipes") ..
$items = DB::table("posts")->union($recipes) ..

$query = DB::query()
    ->fromSub($items, "some_query_name");

// Let's paginate!
$query->paginate(5);

I hope this helps!

Answer 4

The accepted answer works great for Query Builder.

But here's my approach for Laravel Eloquent Builder.

Assume that we're referring to same Model

$q1 = Model::createByMe();       // some condition
$q2 = Model::createByMyFriend(); // another condition

$q2->union($q1);
$querySql = $q2->toSql();

$query = Model::from(DB::raw("($querySql) as a"))->select('a.*')->addBinding($q2->getBindings());

$paginated_data = $query->paginate();

I'm using Laravel 5.6