K. Group customers by LastName and then by FirstName.

L. Count the number of customers having each combination of LastName and FirstName

M. Show the LastName, FirstName, and Phone of all customers who have had an order with Total greater than $100. Use a subquery. Present the results sorted by LastName in ascending order and then FirstName in descending order.

N. Show the LastName, FirstName, and Phone of all customers who have had an order with Total greater than $100. Use a join but do not use JOIN ON syntax. Present the results sorted by LastName in ascending order and then FirstName in descending order.

O. Show the LastName, FirstName, and Phone of all customers who have had an order with Total greater than $100. Use a join using JOIN ON syntax. Present the results sorted by LastName in ascending order and then FirstName in descending order.

P. Show the LastName, FirstName, and Phone of all customers who have bought an item named 'Desk Lamp'. Use a subquery. Present the results sorted by LastName in ascending order and then FirstName in descending order.

Q. Show the LastName, FirstName, and Phone of all customers who have bought an item named 'Desk Lamp'. Use a join but do not use JOIN ON syntax. Present the results sorted by LastName in ascending order and then FirstName in descending order.

R. Show the LastName, FirstName, and Phone of all customers who have bought an item named 'Desk Lamp'. Use a join using JOIN ON syntax. Present the results sorted by LastName in ascending order and then FirstName in descending order.

S. Show the LastName, FirstName, and Phone of all customers who have bought an item named 'Desk Lamp'. Use combination of a join using JOIN ON syntax and a subquery. Present the results sorted by LastName in ascending order and then FirstName in descending order.

T. Show the LastName, FirstName, and Phone of all customers who have bought an item named 'Desk Lamp'. Use combination of a join using JOIN ON syntax and a subquery that is different from the combination in question S. Present the results sorted by LastName in ascending order and then FirstName in descending order.

U. Show the LastName, FirstName, Phone, and ItemDescription of all customers who have bought an item named 'Desk Lamp'. Also show the LastName, FirstName, and Phone of all other customers. Present the results sorted by ItemDescription in ascending order, then LastName in ascending order and then FirstName in descending order.

V. Who referred each customer to Marcia's Dry Cleaning? Show columns named CustomerLastName, CustomerFirstName, ReferredByLastName, and ReferredByFirstName. Include the names of customers who were not referred by any other customer in the results of this query.