unsigned in MySQL

unsigned is both non-negative, this type can increase the data length!

For example if tinyint max is 127, that tinyint unsigned max can go to 127 * 2

The unsigned property is only for integral types, whereas the binary property is used only for char and varchar.

Type	Description
tinyint	A very small integer
smallint	Smaller integer
Mediumint	Medium size integer
Int	Standard integer
bigint	Larger integer
Float	Single-precision floating-point number
Double	Double-precision floating-point number
Decimal	A string of floating-point numbers

The name and range of values for each numeric type are shown in table 2.

Type description	Range of values
Tinyint[(m)]	Signed values: 128 to 127 (-27 to 27-1) Unsigned values: 0 to 255 (0 to 28-1) 1 bytes
Smallint[(m)]	Signed values: 32768 to 32767 (-215 to 215-1) Unsigned values: 0 to 65535 (0 to 21 6-1) 2 bytes
Mediumint[(m)]	Signed values: 8388608 to 8388607 (-22 3 to 22 3-1) Unsigned values: 0 to 16777215 (0 to 22 4-1) 3 bytes
Int[(m)]	Signed values: 2147683648 to 2147683647 (-231 to 231-1) Unsigned values: 0 to 4294967295 (0 to 232-1) 4 bytes
Bigint[(m)]	Signed values: 9223372036854775808 to 9223373036854775807 (-263 to 263-1) Unsigned values: 0 to 18446744073709551615 (0 to 264–1) 8 bytes
Float[(M, D)]	Minimum non 0 value: ±1.175494351e-38
double[(M,D)]	Minimum non 0 value: ±2.2250738585072014e-308
Decimal (M, D)	The range of values depends on M and D

Table 2: Value ranges for numeric column types

The amount of storage required for the various types of values is shown in table 3.

Type description	Storage requirements
Tinyint[(m)]	1 bytes
Smallint[(m)]	2 bytes
Mediumint[(m)]	3 bytes
Int[(m)]	4 bytes
Bigint[(m)]	8 bytes
Float[(M, D)]	4 bytes
Double[(M, D)]	8 bytes
Decimal (M, D)	M bytes (MySQL < 3.23), m+2 bytes (mysql > 3.23)

Table 3: Storage requirements for numeric column types

MySQL offers five integral types: tinyint, smallint, mediumint, int, and bigint. int is an abbreviation of integer. These types are different in the range of values that can be represented. Integer columns can be defined as unsigned thereby disabling negative values, which makes the column range above 0. Various types of storage requirements are also different. A type with a large range of values requires a large amount of storage.

MySQL offers three floating-point types: float, double, and decimal. Unlike integers, floating-point types cannot be unsigned, and their range of values differs from integer types, not only because they have the largest value, but also have a minimum value of 0. The minimum value provides a measure of the corresponding type precision, which is important for recording scientific data (and, of course, negative maximum and minimum values).

unsigned in MySQL