INSERT A ROW WITHOUT SPECIFYING A VALUE FOR JOIN_DATE AND CHECK THAT THE NEW ROW DOES HAVE A JOIN_DATE DATE BUT THAT THE OTHER ROWS DO NOT
10. Insert a row without specifying a value for JOIN_DATE and check that the new row does have a JOIN_DATE date but that the other rows do not:
insert into customers(customer_id, customer_status, customer_name,
creditrating) values (3, 'NEW', 'Sid', 'Gold');
select join_date, count(1) from customers group by join_date;