What is the function of the substring function in SQL?

The SUBSTRING function in SQL is used to extract a portion of a string. It allows you to select a specific substring of characters from a string, with the ability to specify both the starting position and the length.

In specific terms, the function of the SUBSTRING function is:

1. Extract a substring from a string starting at a specified position.
2. You can choose the length of the substring to extract, or extract until the end of the string.
3. It can be used to process specific characters in strings, such as dates, times, or other types of data formats.
4. It can be used to format or transform strings.

The SUBSTRING function may have some variations in different database management systems, for example, some systems use the SUBSTR function to achieve the same functionality. Therefore, when using it, the specific database management system needs to be considered to determine the function’s name and syntax.