SQL » Joins
To load associated relations you can simply use join, left_join, or right_join.
Using joins with relations
class Users < ROM::Relation[:sql]
schema(infer: true) do
associations do
has_many :tasks
has_many :posts
end
end
def with_tasks
join(tasks)
end
def with_posts
left_join(posts)
end
end
Using joins with explicit name and options
If you want to have more control, you can pass table name and additional options yourself:
class Users < ROM::Relation[:sql]
schema(infer: true) do
associations do
has_many :tasks
has_many :posts
end
end
def with_tasks
join(:tasks, id: :user_id, priority: 1)
end
def with_posts
left_join(:posts, id: :user_id)
end
end
Using joins with additional options
The second option hash can be used too, if you want to provide more options:
class Users < ROM::Relation[:sql]
schema(infer: true) do
associations do
has_many :tasks
has_many :posts
end
end
def with_tasks
join(:tasks, { id: :user_id }, table_alias: :user_tasks)
end
def with_posts
left_join(posts, { id: :user_id }, table_alias: :user_posts)
end
end
Learn more
Check out API docs: