Is `IS NULL` the Only Reliable Way to Check for NULL Values in SQL?

Differences and best practices between IS NULL and = NULL in SQL

Although IS NULL and = NULL in SQL look similar, they behave completely differently in queries. In three-valued logic, the result of = NULL is unknown, while IS NULL checks for null values ​​explicitly. Understanding the subtle differences between them is critical to obtaining accurate query results.

When to use IS NULL?

IS NULL is used to clearly determine whether the field is empty. Returns True if the field is empty; False otherwise. It is recommended to test for null values ​​in specific columns to filter out rows containing missing data.

Example:

SELECT * FROM table_name
WHERE field_name IS NULL;

When to use = NULL?

Although = NULL looks like it is used to test for null values, it does not provide precise results. = NULL does not return True or False, but an unknown value, so it is unreliable. It is generally not recommended to use = NULL in queries.

Summary:

Although these two operators are superficially similar, they serve different purposes. IS NULL Explicitly check for null values ​​and provide accurate results. = NULL should be avoided as it produces unknown results and may lead to incorrect query results. Understanding the difference between them allows developers to handle null values ​​efficiently and ensure accurate retrieval of data in SQL queries.

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