Question

class User

    include DataMapper::Resource

    property :id,              Serial
    property :name,            String
    property :email,           String

    has n, :records

end


class Project
    include DataMapper::Resource

    property :id,          Serial
    property :name,        String

    has n, :records ?????

end
#
class Record

   # SPEND_REGEX = /^[0-9]{1}:[0-5]{1}[0-9]{1}$/

    include DataMapper::Resource


    property :id,                Serial
    property :reporting_type,    String
    property :spend_time,        String

    belongs_to :user
    belongs_to :project ????


end

  DataMapper.auto_upgrade!

With ??? I marked relation that throws an error “`execute_non_query’: Cannot add a NOT NULL column with default value NULL (DataObjects::SyntaxError)
”
How to define 2 has many relationships to one model in datamapper?

Answer 1

By default, your belongs_to relationships are required. I assume you already have Record entries in your database. The auto_upgrade is trying to add the new field for the association, and by default it marks that column as NOT NULL. However, for all the existing records, that value will be NULL.

To get around this, do one of the following:

• Do an auto_migrate instead of auto_upgrade. This will blow away your data, but
  will allow you to add the relationship columns without it choking on
  NULL values.
• Make the associations optional with :required => false. This will allow NULLs in the database. Next, go in and set those fields to the appropriate values. Lastly, modify the database table column to be NOT NULL.