SELECT COUNT (DISTINCT ID) FROM teaches WHERE semester  =  'Spring' AND YEAR  =  2010
Find the total number of instructors who teach a course in the Spring 2010 semester.
SELECT COUNT ( DISTINCT ID ) FROM teaches WHERE semester = 'Spring ' AND YEAR = 2010
select count ( distinct id ) from teaches where semester = value and year = value
Find the total number of instructors who teach a course in the Spring 2010 semester .