This is an optional attribute for a column definition of a numeric data type. By default, all numeric columns store SIGNED values, the use of UNSIGNED can increase the range when only positive INTEGER values are needed.
The following table shows the maximum range of values for SIGNED and UNSIGNED numeric data types.
| Datatype | SIGNED | UNSIGNED |
|---|---|---|
| TINYINT | -128 to 127 | 0 to 255 |
| SMALLINT | -32768 to 32767 | 0 to 65535 |
| MEDIUMINT | -8388608 to 8388607 | 0 to 16777215 |
| INT | -2147483648 to 2147483647 | 0 to 4294967295 |
| BIGINT | -9223372036854775808 to 9223372036854775807 | 0 to 18446744073709551615 |
For more information see the MySQL Reference Manual Numeric Types.
