Tricky~21min
The Validated Ticket That Still Got Billed
10 parking sessions were charged an exit fee even though the merchant validation was still valid at exit time — the gate isn't checking validation status before charging. 20 more sessions were also charged despite having a validation on file, but that validation had already expired before the customer left, so charging those is correct.
Tables you'll query
parking_sessionsvalidations
What you'll learn
JOINsDate & Time Functions