Are J.K. Rowling interviews Harry Potter canon? What happens to canon if there's a discrepancy with the book? [duplicate]

Question

It seems that a lot of Harry Potter questions (including my last one) are answered based on tidbits of info that J.K. Rowling provided in various interviews.

I have two related questions (I'll post them separately):

Question #2 of 2. If there ever is a discrepancy between what JKR states in an interview, and a book, which one is considered canon? Book? JKR? Whatever is later?

(What made me think about this was the whole thing with George Lucas and his multiple layers of canon and the whole "L'État c'est moi" Luis-the-14th schtick he has).

Answer 1

Whether JK Rowling interviews and other sanctioned material (such as Pottermore) is considered canon is going to vary based on the reader. Some readers consider only the books to be canon. Others accept interviews and Pottermore as canon. Some even accept the movies. This is subjective; it's going to vary person to person.

Your second question seems a repeat of your previous question, but there are discrepancies in the books and in the interviews. They're called "Flints" after Slytherin Quidditch Captain Marcus Flint, who was the Slytherin Captain Harry's first year, but showed up in the second book. According to JKR he had to repeat his seventh year. So basically she ret-conned.