--- is in

This "set inclusion" notation can be used to simplify certain kinds
   of boolean expressions.  This is useful if you want to select
   based on a combination of fields.

EXAMPLE:

  The condition:    where [job = 'clerk*' and dep_no = 10] or
			  [job = 'programmer*' and dept_no =60]

  becomes:          where <job, dept_no> is in (<'clerk*',      10>,
						<'programmer*', 60>)
