SQL Query

        I have simple question:

                I have a table with several columns, e.g.

			Staff No,
			Department No,
			Post Held    
			Start Date


		For each staff, it is possible to have the same
	department and post with with different start dates. 
	How can I ,say retrieve , those with same staff_no, department
	No and Post Held and yet with the earliest start date or
	the greatest start date?

	Thanks for any hints.

					Anthony HA