What's the Difference Between `= NULL` and `IS NULL` in SQL?

Understanding the Distinction Between " = null" and "IS NULL"

SQL database operations often involve manipulating null values, which represent unknown or missing information. When working with null values, it's essential to understand the difference between using "=" and "IS NULL".

Assigning Null Values using "="

The assignment operator "=" can be used to set a column or variable to null. For instance:

UPDATE TableX SET Column = NULL;

This operation assigns the null value to the "Column" column in the specified table.

Testing for Null Values using "IS NULL"

In contrast to assignment, the "IS NULL" operator is used to check if a value is null. Null values have a unique characteristic that prevents them from being compared directly using the equality operator "=".

In a WHERE clause, using "=" to compare a column to null will always result in false. Instead, you must use "IS NULL":

SELECT * FROM TableX WHERE Column IS NULL;

This query will retrieve rows where the "Column" column contains null values.

Usage Summary

• " = null": Assigns the null value to a column or variable.
• "IS NULL": Tests if a column or variable contains a null value.

Additional Considerations

• The "IS NOT NULL" operator can be used to negate the "IS NULL" condition.
• It's important to understand the special nature of null values and how they interact with SQL operators to avoid erroneous comparisons.

Understanding the distinction between " = null" and "IS NULL" is crucial for accurately manipulating data and querying databases effectively.

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