Question

我希望在this Django example和Postgres中以多对多关系存储额外数据，类似于Sequel。

在我的例子中，每个人都有自己工作的地方，以及他们在那里工作的时间。每个人可以在同一个地方工作不同的时间。例如......

Joe works at The Bar Mon, Wed & Fri 9-5pm.
Joe also works at The Bar Saturday noon-midnight.
Joe works at Some Pub Sunday 12-5.
Joe started working at The Bar 2013-12-07
Joe started working at Some Pub 2014-12-23

我想知道如何设置表格和模型以使其尽可能不尴尬。目前我有这样的架构。

create_table(:people) do
    primary_key :id
    String      :name
end

create_table(:works) do
    primary_key :id
    String      :name
end

create_table(:employments) do
    primary_key :id

    foreign_key :work_id,   :work,   null: false,
    foreign_key :person_id, :people, null: false,

    Date :started
end

create_table(:hours) do
    primary_key :id

    foreign_key :employment_id, :employments, null: false

    String    :dow,    null: false,
    Time      :start,  null: false, only_time: true
    Time      :end,    null: false, only_time: true
end

我应该如何创建模型关联以将它们连接在一起？理想情况下，我希望能够说出像......

joes_hours_at_some_pub = joe.employment("Some Pub").hours

...无需通过中间联接表。

Answer 1

Sequel's advanced association doc就是一个例子。定义就业模型并使用：join_table通过它创建关系。

class Person < Sequel::Model
    one_to_many  :employments,
    many_to_many :works, join_table: :employments

    # This allows joe.employment(work).hours
    def employment(work)
        employments_dataset.where(work_id: work.id)
    end
end

class Work < Sequel::Model
    one_to_many  :employments,
    many_to_many :people, join_table: :employments
end

class Employment < Sequel::Model
    many_to_one  :person
    many_to_one  :work

    one_to_many  :hours
end

class Hours < Sequel::Model
    many_to_one  :practice
end

多对多关系中的数据

1 个答案: