instance method change_column_sql

# File activerecord/lib/active_record/connection_adapters/abstract_mysql_adapter.rb, line 754
      def change_column_sql(table_name, column_name, type, options = {})
        column = column_for(table_name, column_name)

        unless options_include_default?(options)
          options[:default] = column.default
        end

        unless options.has_key?(:null)
          options[:null] = column.null
        end

        td = create_table_definition(table_name)
        cd = td.new_column_definition(column.name, type, options)
        schema_creation.accept(ChangeColumnDefinition.new(cd, column.name))
      end