/* Query 9 (page 137, 223 of the text book)

   Select all employees SSNs.

   The result must be
	'123456789'
	'333445555'
	'999887777'
	'987654321'
	'666884444'
	'453453453'
	'987987987'
	'888665555'
*/

  select ssn
  from employee;
