What are the best practices for handling NULL values in SQL?

What are the best practices for handling NULL values in SQL?

When handling NULL values in SQL, it's important to use IS NULL and IS NOT NULL for checks, and consider using COALESCE to provide default values.

Can you explain how COALESCE works?

COALESCE returns the first non-null value in a list of arguments. For example, COALESCE(column1, column2, 'default') will return the first non-null value from column1 or column2, or 'default' if both are NULL.

What about using NULL in JOIN operations?

In JOIN operations, NULL values can affect the results. Use LEFT JOIN to include rows with NULLs from the left table, and be cautious with INNER JOIN as it will exclude those rows.

Are there any performance considerations with NULL values?

Yes, NULL values can impact performance, especially in indexing. It's often better to avoid NULLs in indexed columns when possible.