MySQL: numeric type, mysql numeric type

MySQL: numeric type, mysql numeric type

Column Type:

1. numeric type

• Integer type:

Type	Bytes occupied	Minimum value (Signed/unsigned)	Maximum value (Signed/unsigned)
TINYINT	1	-128/0	127/255
SMALLINT	2	-32768/0	32767/65535
MEDIUMINT	3	-2147483648/0	214748647/4294967295
INT	4	-2147483648/0	2147483647/4294967295
BIGINT	8	-9223372036854775808/0	9223372036854775807/18446744073709551615

 

 

 

 

 

Tip: You can use the unsigned flag when defining it. If it is not written, it is considered as signed.

Example of inserting a value in the correct range in the table tb_int:

When you try to insert a value out of the range, the following error occurs:

In addition to defining the preceding numeric types, you can also define the display width (to achieve unified display by specifying the display width ).

Format: type (M) M indicates the minimum display width

This attribute usually requires leading zero padding to achieve the goal and become zerofill.

Add column c to tb_int, and set the display width to at least 2;

Insert the following data and observe the results:

Boolean bool type, equivalent to the alias of tinyint (1. MySQL considers 0 as false, and a non-0 value as true.

• Decimal type (floating point + fixed point)

Floating Point Number (decimal point can be changed ):

Single precision (4 bytes): float (about 6 digits by default)

Double Precision (8 bytes): double (about 16 digits by default)

Supported scientific Notation: 123.56*10 ^ 3 should be written in the form of 123.56E3

You can create a table tb_2 as follows:

In fact, when creating a table tb_2, another method is usually used to control the value range:

Float (5, 2) indicates the number of input values in the column a. The total number of digits cannot exceed 5, with a maximum of 2 decimal places and a maximum of 3 integers;

Double (8, 3.

When you enter two numbers that meet the preceding requirements, the output is as follows:

The range of values that float (999.99) can represent is ~ 999.99.

Insert data in scientific notation. The displayed results are as follows:

Fixed number of digits (fixed decimal places): The number of digits is not stored in the exact number of bytes, but is extended (approximately every 9 digits, 4 bytes)

Decimal (M, D): M indicates the total number of digits, D indicates the number of decimal places, and the range also exists. Controlled by M and D

M is 10 by default, and D is 0 by default.

 

Both fixed points and floating point numbers support zerofill, and floating point numbers also support unsigned.