Laravel OrderBy OneToMany Relation - mysql

Question

I have 2 tables events_users:
Which stores information about people that have attended certain events. Many people attend many events, hence using this linking table.
+--------+---------+---------+
| eid | user_id | slot_no |
+--------+---------+---------+
| event1 | user1 | 0 |
| event1 | user2 | 1 |
| event2 | user3 | 0 |
+--------+---------+---------+
And events_user_score:
Which records the different scores of people at the events. At different events there can be lots of different score types, which is why this is in its own table, rather than as columns in the first table
+--------+---------+------------+--------+
| eid | user_id | score_type | number |
+--------+---------+------------+--------+
| event1 | user1 | 1 | 4 |
| event1 | user1 | 2 | 3 |
| event2 | user3 | 1 | 6 |
| event1 | user1 | 2 | 5 | <- this row could not exist as
+--------+---------+------------+--------+ no duplicates possible with same eid, user_id & score_type
I'd like to be able to sort a selection of the first table, based on the figures in the second table. So would love to get a join working that would get a result like this. In effect turning score_type into columns, with the number as the value.
+--------+---------+---------+---+---+
| eid | user_id | slot_no | 1 | 2 |
+--------+---------+---------+---+---+
| event1 | user1 | 0 | 4 | 3 |
| event1 | user2 | 1 | | |
| event2 | user3 | 0 | 6 | |
+--------+---------+---------+---+---+
So far i've tried using laravel's "hasMany" but i can't sort using that technique. So am looking at trying a left join of some type, but have got really confused as now i'm not getting any score back:
$attendees = Events_user::whereIn("events_users.eid", $lastWeeksEvents->pluck('eid'))->where("slot_no",">=",0)
->leftJoin('event_user_score', function ($join) {
$join->on('events_users.eid', '=', 'event_user_score.eid')
->where('events_users.uid', '=', 'event_user_score.uid');
})
->get();
Assume that $lastWeeksEvents returns a list of events with the eid's matching those in the first table.
Edit - even though ther are score_types 1 - 6. Let's stick with just trying to get types 1 & 2 as columns. If that makes it any easier?

Answer 1

To get the desired results you can write following in plain SQL as
select e1.*,
max(case when e2.score_type =1 then e2.number else 0 end ) score_type1,
max(case when e2.score_type =2 then e2.number else 0 end ) score_type2
from events_users e1
left join events_user_score e2 on e1.eid = e2.eid
and e1.user_id = e2.user_id
group by e1.eid, e1.user_id,e1.slot_no
Demo
The above query assumes that there can be two score_types as 1 & 2 if there are more the above query will not be feasible for such type of resultset.
The same using laravel's query builder can be written as.
$attendees = Events_user::from('events_users as e1')
->select(DB::raw("e1.*,max(case when e2.score_type =1 then e2.number else 0 end ) score_type1, max(case when e2.score_type =2 then e2.number else 0 end ) score_type2"))
->leftJoin('events_user_score as e2', function ($join) {
$join->on('e1.user_id', '=', 'e2.user_id');
})
->groupBy('e1.eid')
->groupBy('e1.user_id')
->groupBy('e1.slot_no')
->get();
The above solution join events_users table with your second table events_user_score by matching event and user. The aggregation is involed to get unique data per eid,user_id & slot_no

Answer 2

You could also use a subquery as follows:
Plain SQL:
select u.eid, u.user_id, u.slot_no,
(select number from events_user_score s where s.eid = u.eid and s.user_id = u.user_id and s.score_type = 1) as `1`,
(select number from events_user_score s where s.eid = u.eid and s.user_id = u.user_id and s.score_type = 2) as `2`
from events_users u
Now, using that in Laravel:
//Get all score types
$score_types = DB::table('events_user_score')
->select('score_type')
->groupBy('score_type')
->get();
$event_query = Events_user::from(DB::raw('events_users u'))
->select('eid', 'user_id', 'slot_no');
//Add score types as sub queries
foreach ($score_types as $score) {
$event_query->addSelect(DB::raw('(select number from events_user_score s where s.eid = u.eid and s.user_id = u.user_id and s.score_type = ' . $score->score_type . ') as `' . $score->score_type . '`'));
}
//Example, to sort by score type 1
$data = $event_query->orderBy('1')->get();
Remember to add use DB; at the top of your code.