Laravel Fluent Query Builder Join with subquery

Question

Okay after hours of research and still using DB::select I have to ask this question. Because I am about to trough my computer away ;).

I want to get the last input of a user (base on the timestamp). I can do this with the raw sql

SELECT  c.*, p.* FROM    users c INNER JOIN (   SELECT  user_id,           MAX(created_at) MaxDate   FROM    `catch-text`   GROUP BY user_id  ) MaxDates ON c.id = MaxDates.user_id INNER JOIN     `catch-text` p ON   MaxDates.user_id = p.user_id      AND MaxDates.MaxDate = p.created_at 

I got this query from another post here on stackoverflow.

I have tried everything to do this with the fluent query builder in Laravel however with no success.

I know the manual says you can do this:

DB::table('users')     ->join('contacts', function($join)     {         $join->on('users.id', '=', 'contacts.user_id')->orOn(...);     })     ->get(); 

But that is not helping much because I do not see how I could use a subquery there? Anyone who can light up my day?

Answer 1

Ok for all of you out there that arrived here in desperation searching for the same problem. I hope you will find this quicker then I did ;O.

This is how it is solved. JoostK told me at github that "the first argument to join is the table (or data) you're joining.". And he was right.

Here is the code. Different table and names but you will get the idea right? It t

DB::table('users')         ->select('first_name', 'TotalCatches.*')          ->join(DB::raw('(SELECT user_id, COUNT(user_id) TotalCatch,                DATEDIFF(NOW(), MIN(created_at)) Days,                COUNT(user_id)/DATEDIFF(NOW(), MIN(created_at))                CatchesPerDay FROM `catch-text` GROUP BY user_id)                TotalCatches'),          function($join)         {            $join->on('users.id', '=', 'TotalCatches.user_id');         })         ->orderBy('TotalCatches.CatchesPerDay', 'DESC')         ->get(); 

Answer 2

I was looking for a solution to quite a related problem: finding the newest records per group which is a specialization of a typical greatest-n-per-group with N = 1.

The solution involves the problem you are dealing with here (i.e., how to build the query in Eloquent) so I am posting it as it might be helpful for others. It demonstrates a cleaner way of sub-query construction using powerful Eloquent fluent interface with multiple join columns and where condition inside joined sub-select.

In my example I want to fetch the newest DNS scan results (table scan_dns) per group identified by watch_id. I build the sub-query separately.

The SQL I want Eloquent to generate:

SELECT * FROM `scan_dns` AS `s` INNER JOIN (   SELECT x.watch_id, MAX(x.last_scan_at) as last_scan   FROM `scan_dns` AS `x`   WHERE `x`.`watch_id` IN (1,2,3,4,5,42)   GROUP BY `x`.`watch_id`) AS ss ON `s`.`watch_id` = `ss`.`watch_id` AND `s`.`last_scan_at` = `ss`.`last_scan` 

I did it in the following way:

// table name of the model $dnsTable = (new DnsResult())->getTable();  // groups to select in sub-query $ids = collect([1,2,3,4,5,42]);  // sub-select to be joined on $subq = DnsResult::query()     ->select('x.watch_id')     ->selectRaw('MAX(x.last_scan_at) as last_scan')     ->from($dnsTable . ' AS x')     ->whereIn('x.watch_id', $ids)     ->groupBy('x.watch_id'); $qqSql = $subq->toSql();  // compiles to SQL  // the main query $q = DnsResult::query()     ->from($dnsTable . ' AS s')     ->join(         DB::raw('(' . $qqSql. ') AS ss'),         function(JoinClause $join) use ($subq) {             $join->on('s.watch_id', '=', 'ss.watch_id')                  ->on('s.last_scan_at', '=', 'ss.last_scan')                  ->addBinding($subq->getBindings());                    // bindings for sub-query WHERE added         });  $results = $q->get(); 

UPDATE:

Since Laravel 5.6.17 the sub-query joins were added so there is a native way to build the query.

$latestPosts = DB::table('posts')                    ->select('user_id', DB::raw('MAX(created_at) as last_post_created_at'))                    ->where('is_published', true)                    ->groupBy('user_id');  $users = DB::table('users')         ->joinSub($latestPosts, 'latest_posts', function ($join) {             $join->on('users.id', '=', 'latest_posts.user_id');         })->get();