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