I'm trying to integrate tmdb API in my project. I'm confusing to implement table relationship between movies and collections.

Possibility.

• A movie or TV show can only be included in a specific collection. eg. Iron man 1,2,3 are in a collections called "Iron Man Movies". And it can not be added in a collection called "Marvel Cinematic Universe".
• A movie or TV show can be included in one or more collections by the contributors preferences. eg. Iron man 1, 2, 3 can be in a collection called "Iron Man Movies". And on the other hand it can also be in a collection called "Marvel Cinematic Universe". So that could be many-to-many relationship.

Which one should preferred?

1. One to Many
2. Many to Many