Laravel eloquent select first row of each group by

My problem is solved by @zerofl4g's help.

This eloquent helped by @zerofl4g.

$query->select(DB::raw("SELECT MIN(id), name, subj_id FROM tutorials WHERE completed = 0 GROUP BY subj_id"));

It doesn't work for me but help me a lot. I don't know the precise reason why not worked form me but I think I am using it as subquery. So I got duplicate select and from errors. It must surely work for someone who want to use as single query.

My solution is just select columns with DB::raw and ->from('tutorials') is also optional, as it is subquery of a long query

$query->select(DB::raw('MIN(id) as id, name, subj_id'))->from('tutorials')->where('completed', false)->groupBy('subj_id');

Final eloquent I am using is

$query->select(DB::raw('MIN(id) as id, name, subj_id'))->where('completed', false)->groupBy('subj_id');`

Hope to be helpful.

If you want to return first row in group by, you can try the code below. I think what you want to get is the latest chapter in the subject that not finish.

$data = Tutorial::where('completed', 0)->get();$groups = $data->groupBy('subj_id');$results = [];foreach($groups as $group) {    $results[] = head($group);}return $results;

1. Get all tutorials row

2. Then, group by subj_id. The data you get is like below

{    1: [{        id: "2",        name: "chapter 2",        subj_id: "1",        completed: "0"    }, {        id: "3",        name: "chapter 3",        subj_id: "1",        completed: "0"    }],    2: [{        id: "6",        name: "chapter 3",        subj_id: "2",        completed: "0"    }, {        id: "7",        name: "chapter 4",        subj_id: "2",        completed: "0"    }]}

3. Foreach each group and get the minimum id by using head() helper function in laravel.

Correct query will be like

$query->where('completed', false)->get()->groupBy('subj_id');

get() will be call first before groupBy. I mean once get() make collection you can use all collection method. for more details and know all collection method https://laravel.com/docs/5.8/collections#method-groupby