String_agg用于多列

Question

I have the following select

$repairs = DB::select(DB::raw('
            select r.id repair_id, w.name, w.surname
                from repairs r
                    join repair_worker rw on r.id = rw.repair_id
                    join workers w on w.id = rw.worker_id
                where r.vehicle_id = ?
                group by w.name, w.surname, r.id
           '),[$vehicle->id]);

and I am trying to get w.name and w.surname into one field, separated by a comma for example. There is a function string_agg(column, ',') but I am having no luck to get it working. I always get syntax error.

My try:

$repairs = DB::select(DB::raw('
                select r.id repair_id, string_agg(w.name, w.surname, ', ') workers
                    from repairs r
                        join repair_worker rw on r.id = rw.repair_id
                        join workers w on w.id = rw.worker_id
                    where r.vehicle_id = ?
                    group by r.id
          '),[$vehicle->id]);

How would you do it?

I am using the newest Postgresql 9+

Answer 1

Use the || operator to perform string concatenation, then aggregate this result.

$repairs = DB::select(DB::raw("
    select r.id repair_id, string_agg(w.name || ' ' || w.surname, ', ') workers
    from repairs r
        join repair_worker rw on r.id = rw.repair_id
        join workers w on w.id = rw.worker_id
    where r.vehicle_id = ?
    group by r.id
    "),[$vehicle->id]);