I just signed up for codecademy and started browsing the contents. I decided to have a look at SQL, and as I was going through the details, I believe I might have found an error? (on this page: Key Concepts ).
It says that " There can be only one
PRIMARY KEY column per table and multiple
UNIQUE columns.". As far as I know you can have composite keys which can use 2 or more columns to form a primary key.
CREATE TABLE voting ( QuestionID NUMERIC, MemberID NUMERIC, PRIMARY KEY (QuestionID, MemberID) );
Correct me if I’m wrong.