Learning MySQL and MariaDB

Chapter 10. String Functions

A string is a value that can contain alphabetical characters, digits, and other characters (e.g., the ampersand, the dollar sign). Although a string can contain numbers, they are not considered numeric values. It’s a matter of context and perspective. For instance, postal codes in the United States are all digits, but you shouldn’t store them as integers because the postal code for 02138 would become 2138. You should use a string to store the postal code.

To make the handling of strings easier, MySQL provides many built-in functions. You can format text for nicer results, make better expressions in a WHERE clause, or otherwise extract and manipulate data from a string or column. Therefore, in this chapter, we’ll go through several string functions, grouping them by similar features, and provide examples of how they might be used.

Basic Rules for Using Functions

There are a few things to remember when using functions. String functions also have some conventions of their own. Some of these rules can be different depending on how your server is configured:

• The basic syntax of a function is to a keyword immediately followed by arguments in parentheses. You cannot generally have a space between the keyword and the opening parenthesis like you can with operators in SQL statements (e.g., IN () within a WHERE clause).

• Some functions take no arguments, such as NOW(), which returns the current date or time. Other functions accept a particular number of arguments. Arguments ...