Oracle Database Foundations

A.5. Chapter 5

1. Add a clause to the WHERE condition to make the following query return only the department names without employees:

   select employee_id "Emp ID", last_name || ', ' ||
     first_name "Name", department_name "Dept"
   from employees e,departments d
   where e.department_id(+) = d.department_id;

   Answer: The following clause added to the WHERE condition makes the query return only department names without employees:

   and employee_id is null

2. A type of query that has either too few or no join conditions is known as a ___________ query.

   Answer: Cartesian product

3. Name three kinds of equijoins.

   Answer: Inner joins, self-joins, left outer joins, right outer joins, and full outer joins are all examples of equijoins.

4. A natural join makes what assumption between ...