Show all the invoices for the city Chicago in the state Illinois!
select * from invoices where billing_city = "Chicago" and billing_state = "IL";
What is the total invoice?
select sum(total) from invoices where billing_city = "Chicago" and billing_state = "IL";
How about the number of different customers?
select count(distinct customer_id) from invoices where billing_city = "Chicago" and billing_state = "IL";
How about the number of invoices?
select count(*) from invoices where billing_city = "Chicago" and billing_state = "IL";