Eloquent Joins and Sums - laravel

Question

I have 2 tables and would like to get have a query which gets all columns from table 'projects' and several sums from table 'invoices' based on a field 'type'.
projects
+----+--------+------+--------+
| ID | Address| Date | Other |
+----+--------+------+--------+
| 1 | demo | date | other |
| 2 | demo2 | date2| other2 |
invoices
+----+---------+-----+--------+
| ID | proj_id | type| amount |
+--------------+-----+--------+
| 1 | 1 | a | 10 |
| 2 | 1 | a | 20 |
| 3 | 1 | b | 10 |
| 4 | 1 | b | 15 |
| 5 | 1 | c | 5 |
| 6 | 2 | a | 30 |
| 7 | 2 | a | 5 |
| 8 | 2 | b | 30 |
| 9 | 2 | c | 5 |
| 10 | 2 | c | 30 |
Using Laravel Eloquent I want to be able to get:
+----+---------+------+-------+---+---+---+
| ID | Address | Date | Other | a | b | c |
+----+---------+------+-------+---+---+---+
| 1 | demo | date | other |30 |25 | 5 |
| 2 | demo2 | date2| other2|35 |30 |35 |
Im getting stuck with the sum part, well actually the whole thing!
So far I have:
$projects = DB::table('projects')
->leftJoin('invoices', 'projects.id', '=', 'invoices.project_id')
->select('projects.*', 'invoices.*')
->get();
Which is obviously not very far along! Any help would be greatly appreciated!

Answer 1

You need a basic pivot query here. The easiest way to go here would probably be via a raw select:
$sql = "projects.*, ";
$sql .= "sum(case when invoices.type = 'a' then invoices.amount end) as a, ";
$sql .= "sum(case when invoices.type = 'b' then invoices.amount end) as b, ";
$sql .= "sum(case when invoices.type = 'c' then invoices.amount end) as c";
$projects = DB::table('projects')
->select(DB::raw($sql))
->leftJoin('invoices', 'projects.id', '=', 'invoices.project_id')
->groupBy('project.id')
->get();
This should correspond to the following raw MySQL query:
SELECT
p.*,
SUM(CASE WHEN i.type = 'a' THEN i.amount END) AS a,
SUM(CASE WHEN i.type = 'b' THEN i.amount END) AS b,
SUM(CASE WHEN i.type = 'c' THEN i.amount END) AS c
FROM project p
LEFT JOIN invoices I
ON p.id = i.project_id
GROUP BY
p.id;