How many custmers are there?
select count(*) from customers
How many customers are there that have account name 162?
select count(*) from accounts as t1 join customers as t2 on t1.customer_id = t2.customer_id where t1.account_name = "162"
Show his first name, last name, and phone.
select t2.customer_first_name, t2.customer_last_name, t2.customer_phone from accounts as t1 join customers as t2 on t1.customer_id = t2.customer_id where t1.account_name = "162"