IS NULL vs equals NULL in SQL - When to Use Which

The Big Idea

Why does comparing to NULL in SQL never work the way you expect?

The Scenario

Imagine you have a list of customer records in a spreadsheet. Some customers have missing phone numbers, but you want to find all those missing entries. You try to filter by typing "phone = NULL" in the search box, but nothing shows up.

The Problem

Using "equals NULL" in SQL doesn't work because NULL means 'unknown' or 'missing' data, not a value you can compare directly. This makes queries return no results or wrong results, causing confusion and wasted time.

The Solution

The IS NULL condition in SQL is designed to check for missing or unknown values properly. It tells the database to look for entries where the data is absent, making your queries accurate and reliable.

Before vs After

✗ Before

SELECT * FROM customers WHERE phone = NULL;

✓ After

SELECT * FROM customers WHERE phone IS NULL;

What It Enables

Using IS NULL lets you correctly find and handle missing data, making your database queries trustworthy and effective.

Real Life Example

A company wants to send promotional texts but only to customers with phone numbers. Using IS NULL, they can easily exclude customers without phone numbers and avoid sending messages to empty contacts.

Key Takeaways

NULL means missing or unknown data, not a value.

Using = NULL in SQL does not work as expected.

IS NULL is the correct way to check for missing data.