mysql - ActiveRecord associations: am I doing it right? -

i'm working on building simple rails application (this first rails project) tracking statistics users within group. i've created tables using migration script , looks alright when @ in mysql, not of models return data when join them table.

does see wrong models, migration script, or data model?

here migration file script code:

class creategroupsusers < activerecord::migration   def change      create_table :types |t|       t.string :name     end      create_table :groups |t|       t.string :name       t.belongs_to :type, index: true     end      create_table :users |t|       t.string :username       t.string :email       t.string :first_name       t.string :last_name       t.string :e_password       t.string :salt       t.timestamps     end      create_table :roles |t|       t.string :name     end      create_table :groups_users, id: false |t|       t.belongs_to :group, index: true       t.belongs_to :user, index: true       t.belongs_to :role, index: true     end      create_table :statistics |t|       t.string :name     end      create_table :groups_users_statistics, id: false |t|       t.string :value       t.belongs_to :group, index: true       t.belongs_to :user, index: true       t.belongs_to :statistic, index: true     end    end end 

here my models:

class type < activerecord::base     has_many :groups end  class role < activerecord::base     has_many :groups_users end  class user < activerecord::base     has_and_belongs_to_many :groups     has_one :roles, through: :groups_users end  class group < activerecord::base     has_and_belongs_to_many :users     has_one :types end  class statistic < activerecord::base     //i'm not sure how define model end 

and here's data model

i updated models per esse, pavan , andyv's comments. seems working fine now

class type < activerecord::base     has_many :groups end  class role < activerecord::base     has_many :group_users end  class user < activerecord::base     has_many :group_users     has_many :groups, through: :group_users      has_many :group_user_statistics     has_many :groups, through: :group_user_statistics     has_many :statistics, through: :group_user_statistics end  class group < activerecord::base     has_many :group_users     has_many :users, through: :group_users      has_many :group_user_statistics     has_many :users, through: :group_user_statistics     has_many :statistics, through: :group_user_statistics end  class groupuser < activerecord::base     belongs_to :group     belongs_to :user end  class statistic < activerecord::base     has_many :group_user_statistics     has_many :groups, through: :group_user_statistics     has_many :users, through: :group_user_statistics end  class groupuserstatistic < activerecord::base     belongs_to :user     belongs_to :group     belongs_to :statistic end