Just posted a question about room in stackoverflow, it's about an M:N relationship, if you know or have worked with it, please ping me, I'm seeing that I'm almost done but I need my last clarification. Thanks!

Link?

Send it to you

Haven't used Room in a while. Not sure if M:N is now supported. You may have to manually write the query.

Easier question then, I have inside my Entity an object that is a List<String> so I need to do a query to check if X is inside that list, how can I do it?

The version of sqlite shipped with android can't handle surgical queries on a column. You'll have to move that list into another table and do JOINs and WHEREs.

i'm usin room

Which uses sqlite underneath.

Then how can I do the query to that list?

Look at Option #1 of the voted answer.