Final answer:
The 'IS NULL' comparison operator is used to search for NULL values, especially in SQL queries within databases where it's important to distinguish fields with no data.
Step-by-step explanation:
The IS NULL comparison operator is used to search for NULL values. When working with databases, it's necessary to check if a column has a NULL value, which signifies that the field has no data stored in it. This is particularly important in SQL queries since NULL is not equal to zero or an empty string—it is a unique marker for missing or unknown data. To test for NULL, you do not use the standard comparison operators like = or !=. Instead, you use the IS NULL or IS NOT NULL syntax within your WHERE clause.
For example, to find all records in a customers table where the email address is not provided, you would write:
SELECT * FROM customers WHERE email IS NULL;
This would return only the rows where the email column is NULL, effectively excluding all rows with an email address.