Iīm just reading a course in databases and I got my examresult back yesterday and I didnīt get through.
The big problem is that what I read about normalizations is that you should avoid redundance.
In this case, where we get the answer together with the exam i just donīt get the logic, because there would be A LOT of redundance with date, time and seat.
Isnīt the rule "avoid redundance" the first rule of normalization or am I thinking all wrong?
Normalization isn't concerned with redundant values, it's meant to reduce redundant associations between values. Values that are recorded multiple times are perfectly normal if they're involved in multiple relationships. However, when a functional or multivalued dependency (one-to-one or one-to-many relationship) is recorded more than once, there's a risk that only some of the rows could be updated, causing inconsistent data.
In your example, see in the 1NF table how filmId -> filmName is recorded multiple times, so too personNr -> name, telephone, as well as (date, time, seatNr) -> personNr and (date, time) -> filmId. When normalizing, we look for patterns of duplication between related columns, not just in one column.