MySQL integer type from integer range

mysql_int_type.rb

def mysql_int_type(int_range)
  case 
  when (0..255)                                     .cover?(int_range) then "tinyint unsigned"
  when (0..65535)                                   .cover?(int_range) then "smallint unsigned"
  when (0..16777215)                                .cover?(int_range) then "mediumint unsigned"
  when (0..4294967295)                              .cover?(int_range) then "int unsigned"
  when (0..18446744073709551615)                    .cover?(int_range) then "bigint unsigned"
  when (                 -128..127)                 .cover?(int_range) then "tinyint"
  when (               -32768..32767)               .cover?(int_range) then "smallint"
  when (             -8388608..8388607)             .cover?(int_range) then "mediumint"
  when (          -2147483648..2147483647)          .cover?(int_range) then "int"
  when ( -9223372036854775808..9223372036854775807) .cover?(int_range) then "bigint"
  else                                                                      "varchar(#{int_range.last.to_s.length})"
  end
end