What is the function of the substring function in MySQL?

The SUBSTRING function in MySQL is used to extract a substring from a string. Its purpose is to extract a substring from a string based on a specified starting position and length. The specific usage is as follows:

SUBSTRING(str, start, length)

Parameter Description: str: the string from which the substring needs to be extracted. start: the starting position of the substring, counting from 1. length: the length of the substring. If no length is specified, all characters from the starting position to the end of the string will be extracted. Example: Assuming there is a string ‘Hello World’, the SUBSTRING function can be used to extract a substring from it.

1. SUBSTRING('Hello World', 1, 5) --> 'Hello'，从起始位置开始提取5个字符。
2. SUBSTRING('Hello World', 7) --> 'World'，从起始位置开始提取到字符串末尾的所有字符。

The SUBSTRING function in MySQL is very helpful for extracting specific portions of information from long strings.