10.23.17
cartesian product (all. 5 prof 23 clas. 115 total).
join predicate - get rid of all unnecessary rows. Where clause where by we put
common attributes values equal to one another.
join - product w/ project && select
course go down to class
10.25.17
don't mix agg. funtions w/ regular
unless.... using group by such as
from clause with more than one table is a join without a predicate, and is nasty
it's a cartesian product, when i dont do select & project
//Distinct does not mean repeat