Tell me the number of tests with result "Pass".
select count(*) from student_tests_taken where test_result = "Pass"
Tell me the number of tests with result "Fail".
select count(*) from student_tests_taken where test_result = "Fail"
List each test result and its count in descending order of count.
select test_result, count(*) from student_tests_taken group by test_result order by count(*) desc