MySQL floating point precision range and rounding

Question

Answer 1

Because when you created the table, you specified f3 as float(6,2), so what do these 6 and 2 mean?
6 is the total number of digits. 2 means only 2 digits are retained after the decimal point. So it will be displayed as 9999.99, which is a total of 6 9s, and there are 2 digits after the decimal

Answer 2

It is recommended to use decimal, especially when it comes to money issues. In mysql, float and double (or real) are floating point numbers, and decimal (or numberic) is a fixed point number.

The advantage of floating-point numbers over fixed-point numbers is that when the length is certain, floating-point numbers can represent a larger data range; its disadvantage is that it can cause accuracy problems.

In future applications of floating-point numbers and fixed-point numbers, everyone should remember the following points:

1. There is an error problem in floating point numbers;

2. Accuracy-sensitive data such as currencies should be represented or stored in fixed-point numbers;

3. In programming, if floating point numbers are used, special attention should be paid to error issues and try to avoid floating point comparisons;

4. Pay attention to the handling of some special values ​​in floating point numbers.
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Answer 3

float(m,d) In, m represents the total number of digits, d represents the number of digits to the right of the decimal point

create table example3 (
    f1 float,
    f2 float(5,2),
    d1 double,
    d2 double(5,2)
);

insert into example3(f1, f2, d1, d2)
            values(3.141592657,3.141592657,3.141592657,3.141592657),
                  (3,3,3,3);

Displayed as follows:

f1	f2	d1	d2
3.14159	3.14	3.141592657	3.14
3	3.00	3	3.00

Explanation:

• Not specified m,d: Take the value according to the range of float and double

• Specify m,d ： 按照 m,d: Take it according to the value of

  . If it exceeds, it will be rounded. If it does not exceed, it will be supplemented with 0

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