SQL queries

A. Find the number of customers who are signed up for at least one type of communication.;B. List the number of customers who are signed up for each communication name.;C. List the names and addresses of customers who have both CHECKING and SAVINGS accounts.;D. List the customer.id of customers who do not have any active bank accounts.;E. Sign up a customer (id=47) for SMS_ALERT by inserting a new row in communication_channel.