```ruby
module ActiveRecord #:nodoc:
  module ConnectionAdapters #:nodoc:
    module OracleEnhancedDirty #:nodoc:

      module InstanceMethods #:nodoc:
        private
        
        def _field_changed?(attr, old, value)
          if column = column_for_attribute(attr)
            # Added also :decimal type
            if (column.type == :integer || column.type == :decimal) && column.null && (old.nil? || old == 0) && value.blank?
              # For nullable integer columns, NULL gets stored in database for blank (i.e. '') values.
              # Hence we don't record it as a change if the value changes from nil to ''.
              # If an old value of 0 is set to '' we want this to get changed to nil as otherwise it'll
              # be typecast back to 0 (''.to_i => 0)
              value = nil
            # Oracle stores empty string '' as NULL
            # therefore need to convert empty string value to nil if old value is nil
            elsif column.type == :string && column.null && old.nil?
              value = nil if value == ''
            else
              value = column.type_cast(value)
            end
          end

          old != value
        end
        
      end

    end
  end
end

if ActiveRecord::Base.method_defined?(:changed?)
  ActiveRecord::Base.class_eval do
    include ActiveRecord::ConnectionAdapters::OracleEnhancedDirty::InstanceMethods
  end
end
```

Address 2 failues since numeric_changes_from_zero_to_string? method implemented at Rails.
user
```ruby
module ActiveRecord #:nodoc:
  module ConnectionAdapters #:nodoc:
    module OracleEnhancedDirty #:nodoc:

      module InstanceMethods #:nodoc:
        private
        
        def _field_changed?(attr, old, value)
          if column = column_for_attribute(attr)
            # Added also :decimal type
            if (column.type == :integer || column.type == :decimal) && column.null && (old.nil? || old == 0) && value.blank?
              # For nullable integer columns, NULL gets stored in database for blank (i.e. '') values.
              # Hence we don't record it as a change if the value changes from nil to ''.
              # If an old value of 0 is set to '' we want this to get changed to nil as otherwise it'll
              # be typecast back to 0 (''.to_i => 0)
              value = nil
            # Oracle stores empty string '' as NULL
            # therefore need to convert empty string value to nil if old value is nil
            elsif column.type == :string && column.null && old.nil?
              value = nil if value == ''
            elsif old == 0 && value.present? && value != '0'
              value = nil
            else
              value = column.type_cast(value)
            end
          end

          old != value
        end
        
      end

    end
  end
end

if ActiveRecord::Base.method_defined?(:changed?)
  ActiveRecord::Base.class_eval do
    include ActiveRecord::ConnectionAdapters::OracleEnhancedDirty::InstanceMethods
  end
end
```
assistant