/* Adding a row number to the output */

/* All databases support -----------------------------------------------------*/

select ROW_NUMBER() OVER(order by lname) AS "row num", fname, lname, course_id 
from   student join class on ssn=stu_ssn;



/* MySql - also --------------------------------------------------------------*/

set     @count:=0;
select (@count:=@count+1) as "row num", fname, lname, course_id
from    student join class on ssn=stu_ssn;



/* Oracle also ---------------------------------------------------------------*/
/* Oracle has a keyword called rownum */

select ROWNUM as "row num", fname, lname, course_id
from   student join class on ssn=stu_ssn;