มูลค่าธุรกรรมเฉลี่ยและยอดรวมคือเท่าไร?ไม่จำเป็นต้องใช้ตารางทั้งหมด
What is the average and total transaction amount?It is not neccessary to use all the tables.
 customers:  customer_id [ number]  customer_first_name [ text]  customer_last_name [ text]  customer_address [ text]  customer_phone [ text]  customer_email [ text]  other_customer_details [ text] 
SELECT AVG(transaction_amount), SUM(transaction_amount) FROM financial_transactions