What is the usage of regexp in SQL?

In SQL, REGEXP is the operator used for regular expression matching. It can be used to search for substrings in a string that match specific patterns. The basic syntax is as follows:

SELECT column_name
FROM table_name
WHERE column_name REGEXP 'pattern';

In this case, column_name is the name of the column to be matched, table_name is the name of the table to be queried, and pattern is the regular expression pattern to be matched. For example, you can use REGEXP to find all strings that start with a letter.

SELECT *
FROM table_name
WHERE column_name REGEXP '^[a-zA-Z].*';

It is important to note that the syntax of regular expressions may vary in different databases, so it is necessary to consult the documentation of the specific database when using REGEXP.