# Children

A parent doesn't declare its children. The relationship is stated once,
on the child's reference. A query that wants a project's todos names that
field, here in an `include:`:

```jadpo
include: {
    todos: Todo.project_id
}
```

It gets a list, since `project_id` isn't unique, or at most one record
when the field is unique. How a query includes records is
[Includes](reads-and-writes.md#includes).

A many-to-many link, such as a project's members, is an entity with two
references and a unique rule over both.