How to use unsigned in mysql
I believe many inexperienced people don't know what to do about how to use unsigned in mysql. Therefore, this article summarizes the causes and solutions of the problem. Through this article, I hope you can solve this problem.
Since unsigned is a non-negative number, you can increase the data length with this type!
For example, if the maximum tinyint is 127, then the maximum tinyint unsigned can be 127x2
The unsigned attribute is only for integers, while the binary attribute is only used for char and varchar.
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Types
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
The floating point number of a string
The name and range of values for each numeric type are shown in Table 2.
Type description
Value range
Tinyint [(m)]
Have symbolic values:-128 to 127 (- 27 to 27-1)
Unsigned values: 0 to 255 (0 to 28-1) 1 byte
Smallint [(m)] www.2cto.com
Have symbolic values:-32768 to 32767
Unsigned values: 0 to 65535 (0 to 21 6-1) 2 bytes
Mediumint [(m)]
Have symbolic values:-8388608 to 8388607 (- 22 3 to 22 3-1)
Unsigned values: 0 to 16777215 (0 to 22 4-1) 3 bytes
Int [(m)]
Have symbolic values:-2147683648 to 2147683647 (- 231 to 231-1)
Unsigned values: 0 to 4294967295 (0 to 4294967295 # 1) 4 bytes
Bigint [(m)]
Symbolic values:-9223372036854775808 to 9223373036854775807 (- 263 to 263-1)
Unsigned values: 0 to 18446744073709551615 (0 to 264-1) 8 bytes
Float [(m, d)]
Minimum non-zero value: ±1.175494351e-38
Double [(m _ m _ d)]
Minimum non-zero value: ±2.2250738585072014e-308
Decimal (m, d)
Variable; the range of values depends on m and d
Table 2: range of values for numeric column types
The amount of storage required for various types of values is shown in Table 3.
Type description www.2cto.com
Storage requirement
Tinyint [(m)]
1 byte
Smallint [(m)]
2 byt
Mediumint [(m)]
3 bytes
Int [(m)]
4 byt
Bigint [(m)]
8 byte
Float [(m, d)]
4 byt
Double [(m, d)]
8 byte
Decimal (m, d)
M bytes (
< 3.23），m+2字节（mysql >3.23)
Table 3: storage requirements for numeric column types www.2cto.com
Mysql provides five integers: tinyint, smallint, mediumint, int, and bigint. Int is the abbreviation of integer. These types are different in the range of representable values. Integer columns can be defined as unsigned to disable negative values; this makes the range of values for the column above 0. Different types of storage requirements are also different. Types with a wide range of values require a larger amount of storage.
Mysql provides three floating-point types: float, double, and decimal. Unlike integers, floating-point types cannot be unsigned, and their range of values is different from integers, not only in that these types have a maximum value, but also a minimum non-zero value. The minimum value provides a measure of the corresponding type of accuracy, which is very important for recording scientific data (of course, there are negative maximum and minimum values).
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