How much did customer 103 pay in total?
Pay in total refers to SUM(amount);
SELECT SUM(t.amount) FROM payments t WHERE t.customerNumber = '103'
database name:db_id car_retails
offices table offices Cols: office code dtype text, city dtype text, phone dtype text, addressLine1 dtype text, addressLine2 dtype text, state dtype text, country dtype text, postalCode dtype text, territory dtype text, 
employees table employees Cols: Employee Number dtype integer, last name dtype text, first name dtype text, extension dtype text, email dtype text, office code dtype text, reports to dtype integer, job title dtype text, 
customers table customers Cols: customer number dtype integer, customer name dtype text, contact last name dtype text, contact first name dtype text, phone dtype text, addressLine1 dtype text, addressLine2 dtype text, city dtype text, state dtype text, postalCode dtype text, country dtype text, sales representative employee number dtype integer, credit limit dtype real, 
orders table orders Cols: order number dtype integer, order date dtype date, required Date dtype date, shipped date dtype date, status dtype text, comments dtype text, customer number dtype integer, 
payments table payments Cols: customer number dtype integer, check Number dtype text, payment Date dtype date, amount dtype real, 
productlines table productlines Cols: product line dtype text, text description dtype text, html description dtype text, image dtype blob, 
products table products Cols: product code dtype text, product name dtype text, product line dtype text, product scale dtype text, product vendor dtype text, product description dtype text, quantity in stock dtype integer, buy price dtype real, Manufacturer Suggested Retail Price dtype real, 
orderdetails table orderdetails Cols: order number dtype integer, product code dtype text, quantity ordered dtype integer, price for each dtype real, order Line Number dtype integer, 
