Understanding the Use of FloatingPoint Data Type in MySQL（mysql浮点型）
来源：https://www.mysqltutorial.org/mysql-floating-point-data-type/
Floating-point data type is a data type used to store floating-point numbers such as decimal fractions or real numbers. It is available in almost every programming language or software package. In MySQL, there are three types of floating-point data types: Float, Double Precision and Floating Point.
Float: This is the simplest of the three, and the type that is most commonly used. It can store four bytes worth of data and can represent a range of values from about 3.4e-38 to 3.4e+38, with six to nine significant digits.
Double Precision: Double precision is similar to its float counterpart, but has eight bytes of storage capacity, allowing it to represent a range of values from about 1.7e-308 to 1.7e+308, with fifteen to eighteen significant digits.
Floating Point: The Floating Point data type is the most complex of the three. It has twelve bytes of storage and can represent a range of values from about 1.18e-4932 to 3.40e+4932, with thirty-seven to forty significant digits.
Since MySQL only allows one floating-point data type per column, it’s important to choose the right type. In most cases it is best to use the Float data type, as it is the most efficient and reliable. The Double Precision and Floating Point data types should be used only when the higher precision is necessary.
It is also possible to perform arithmetic operations on MySQL floating-point data types. For example, to add two Float values, you can use the following statement:
`SELECT FLOAT_VALUE_1 + FLOAT_VALUE_2 FROM table_name;`
The result of this query will be another Floating-point value. Similarly, multiplication, division as well as other arithmetic operations can be performed with the MySQL Floating-point data type.
MySQL also provides some useful functions for working with floating-point data types. For example, the ROUND() function can be used to round a floating-point number to the specified number of decimal places. Similarly, the CEIL() and FLOOR() functions can be used to round a floating-point number up or down, respectively.
In summary, Floating-point data types are an essential part of any relational database and can offer significant benefits over other data types. MySQL offers a number of powerful functions and storage types that will help you work with Floating-point data types and get the best results from your data.
