Which customers owe you money — and how overdue are they?

SELECT
  c.display_name                                         AS customer,
  c.primary_email_addr                                   AS email,
  COUNT(i.id)                                           AS overdue_invoices,
  ROUND(SUM(i.balance)::numeric, 2)                    AS total_owed,
  MAX(CURRENT_DATE - i.due_date::date)                 AS max_days_overdue,
  MIN(i.due_date::date)                                AS oldest_due_date,
  ROUND(AVG(i.balance)::numeric, 2)                    AS avg_invoice_balance
FROM qbo_invoices i
JOIN qbo_customers c ON c.id = i.customer_id
WHERE i.balance > 0
  AND i.due_date::date < CURRENT_DATE
  AND i.transaction_status NOT IN ('Void', 'Deleted')
GROUP BY c.id, c.display_name, c.primary_email_addr
ORDER BY total_owed DESC