# File lib/active_record/connection_adapters/mysql_adapter.rb, line 793
        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

          change_column_sql = "CHANGE #{quote_column_name(column_name)} #{quote_column_name(column_name)} #{type_to_sql(type, options[:limit], options[:precision], options[:scale])}"
          add_column_options!(change_column_sql, options)
          add_column_position!(change_column_sql, options)
          change_column_sql
        end