SQLite trigger analyze row data

I have a database with news articles. Each article has a field "categories" which contains ordinals of categories like "3, 7, 9". My point is to create one more database with fields (_id, article_id, category_id) for many-to-many pattern to provide querying articles by categories.

Is there any way to analyze TEXT field with those numbers from SQLite? To split them by "," and process each number with INSERT. Now I do it with java, but I want to create trigger.