Which SQL function can be used to extract a substring from a string using regular expressions?

The SQL function that can be used to extract a substring from a string using regular expressions is the REGEXP_SUBSTR() function. Here's how you can use it:

Step 1: Identify the string from which you want to extract a substring. This will be the first argument of the function. For example, let's say we have a string 'Hello, World!'.

Step 2: Write the regular expression that matches the substring you want to extract. This will be the second argument of the function. For example, if we want to extract the word 'Hello', the regular expression would be 'Hello'.

Step 3: Use the REGEXP_SUBSTR() function in your SQL query. The syntax is as follows:

REGEXP_SUBSTR(string, pattern)

So, in our example, the query would look like this:

SELECT REGEXP_SUBSTR('Hello, World!', 'Hello');

This query will return 'Hello', which is the substring of the original string that matches the regular expression.