I'm doing the SQL-Courses since today and slowly I'm losing the grip, so I need to start asking questions:
I don't understand how this works in terms of, I understand how subquery works, cause there is clear question: SELECT (Display) FROM airports WHERE elevation < 2000
Where is the connection between the codes and the flights? How does the "main" query know which fly it needs to "display" or to select?
I hope you understand my question.
Thanks in Advance!