mysql to number 函数

MySQL TO_NUMBER Function: A Comprehensive Guide

When working with numeric values in MySQL, you may come across the need to convert a non-numeric value to a number. The TO_NUMBER function in MySQL allows you to do just that. In this article, we will explore the syntax and usage of the TO_NUMBER function, along with some examples to illustrate its functionality.

Syntax of TO_NUMBER Function

The syntax of the TO_NUMBER function in MySQL is as follows:

TO_NUMBER(expression)

Where expression is the value that you want to convert to a number.

Examples of TO_NUMBER Function

Let's look at some examples to understand how the TO_NUMBER function works:

Example 1: Converting a String to a Number

In this example, we will convert a string value to a number using the TO_NUMBER function:

SELECT TO_NUMBER('123') AS number;

The output of this query will be:

number
123

Example 2: Handling Non-Numeric Values

If the expression passed to the TO_NUMBER function is not a valid number, MySQL will return a NULL value. For example:

SELECT TO_NUMBER('abc') AS number;

The output of this query will be:

number
NULL

Example 3: Converting NULL Values

If the expression passed to the TO_NUMBER function is NULL, the function will return NULL. For example:

SELECT TO_NUMBER(NULL) AS number;

The output of this query will be:

number
NULL

Class Diagram

Below is a class diagram illustrating the TO_NUMBER function in MySQL:

classDiagram
    TO_NUMBER --|> expression

Conclusion

In this article, we have explored the TO_NUMBER function in MySQL, which allows you to convert non-numeric values to numbers. We have discussed the syntax and usage of the function, along with some examples to demonstrate its functionality. By using the TO_NUMBER function, you can handle non-numeric values more effectively in your MySQL queries.