/* Oracle only */

/* Display data of all instructors that are not also students */
/* the instructor data MINUS the student data */
/* data exists in one table, but does not exist in a second table */

SELECT fname, lname, ssn
from   instructor

MINUS

SELECT fname, lname, ssn
from   student;



/* Instructors that are not currently teaching a class */

select ssn
from instructor
MINUS
select inst_ssn
from class;



/* MySQL and SQLite do not support MINUS, but you can simulate using an outer join */
/* Instructors that are not currently teaching a class */

SELECT *
from instructor 
left join class 
on ssn = inst_ssn
where inst_ssn is null;