Laravel – How to get SUM of a column in database table

Laravel have DB class to perform raw queries whenever needed instead of Eloquent model. I recommend to use eloquent model in most cases but sometimes we need to perform raw queries. DB class is where we need.

Getting sum of a column in database is fairly simple. See below use case with and without where clause.

$amount = DB::table('invoice_details')
          ->sum('billing_amount');

which gets the sum of the entire column. I tried writing:

$amount = DB::table('invoice_details')
            ->where('invoice_id' '=' $id)
            ->sum('billing_amount');

Make sure SUM method is placed at the end otherwise Laravel may thrown an error.