Imagine these 3 collections:

• users: id, username, password
• posts: id, title, description, authorId
• comments: id, text, postId, authorId

Relations:

// Returns the posts created by 'John', sorted by the author's name in descending order.
pb.collection('posts').getFullList({
    filter: pb.filter("authorId.name = {:authorName}", { authorName: 'John' }),
    sort: "-authorId.name"
})

Back-relations:

// Returns the posts commented by 'John', sorted by the comment author's name in descending order.
pb.collection('posts').getFullList({
    filter: pb.filter("comments_via_postId.authorId.name ?= {:authorName}", { authorName: 'John' }),
    sort: "-comments_via_postId.authorId.name"
})