ประเทศ 5 อันดับแรกตามจำนวนใบแจ้งหนี้และมีกี่ประเทศ?ไม่จำเป็นต้องใช้ตารางทั้งหมด
what are the top 5 countries by number of invoices and how many do they have?It is not neccessary to use all the tables.
 invoices:  id [ INTEGER]  customer_id [ INTEGER]  invoice_date [ TIMESTAMP]  billing_address [ VARCHAR(70)]  billing_city [ VARCHAR(40)]  billing_state [ VARCHAR(40)]  billing_country [ VARCHAR(40)]  billing_postal_code [ VARCHAR(10)]  total [ NUMERIC(102)] 
SELECT billing_country, COUNT(*) FROM invoices GROUP BY billing_country ORDER BY COUNT(*) DESC LIMIT 5