In MySQL, the IS NULL condition is used to check whether a specific column in a table contains a NULL value. NULL is a special marker in the database that indicates the absence of data in a particular field. It is not the same as an empty string or zero; rather, it represents the lack of a value.

Syntax

Here’s an explanation of how to use IS NULL in MySQL:

SELECT column_name(s)
FROM table_name
WHERE column_name IS NULL;

In this syntax:

column_name(s) refers to the column or columns you want to retrieve.
table_name is the name of the table from which you want to retrieve data.
IS NULL is the condition used to filter rows where the specified column has a NULL value.

Example

Consider a simple table named employees with columns like employee_id, employee_name, and hire_date. If you want to find employees whose hire date is not specified (i.e., it’s NULL), you can use the following query:

SELECT employee_id, employee_name
FROM employees
WHERE hire_date IS NULL;

This query will return a list of employees who have no hire date recorded in the database.

Notes

It’s important to use IS NULL rather than = NULL when checking for NULL values in MySQL. The reason is that NULL is not equal to anything, not even to another NULL value. Therefore, you should always use the IS NULL condition for accurate results.

Conversely, if you want to find records where a column is not NULL, you can use the IS NOT NULL condition.

SELECT column_name(s)
FROM table_name
WHERE column_name IS NOT NULL;

In summary, the IS NULL condition is a valuable tool in MySQL for filtering data and retrieving records where a specific column contains NULL values, helping you manage and analyze your database effectively.