SELECT sum(total) FROM invoices WHERE billing_city  =  "Chicago" AND billing_state  =  "IL";
What are the total amount of money in the invoices billed from Chicago, Illinois?
SELECT sum ( total ) FROM invoices WHERE billing_city = `` Chicago '' AND billing_state = `` IL '' ;
select sum ( total ) from invoices where billing_city = value and billing_state = value
What are the total amount of money in the invoices billed from Chicago , Illinois ?