?? Tricky Concept in SQL: NULL Values
Madhu Mitha K
Data-driven Software Engineer proficient in Excel, Power BI, SQL, Azure Data Factory, and Agile methodologies.
Understanding NULL values in SQL is essential for crafting precise and efficient queries. NULL represents the absence of a value, posing unique challenges and considerations in database management.
?? Comparison with NULL: Standard comparison operators like "=", "<", ">" don't yield expected results with NULL. Instead, use "IS NULL" or "IS NOT NULL" for accurate evaluations.
?? Handling NULL in WHERE Clauses: When filtering data, be mindful of NULL values. Utilize "IS NULL" or "IS NOT NULL" to include or exclude NULL values as needed.
?? Aggregate Functions and NULL: Aggregate functions like SUM(), AVG(), COUNT() ignore NULL values in calculations. This behavior demands careful consideration to avoid unexpected outcomes.
?? NULL in Joins: NULL values in join operations can impact result sets. Understanding how NULL affects joins ensures accurate query outcomes.
?? Default Values and NULL: While default values can prevent NULLs, judicious use of NULL values may be more meaningful in certain contexts.
?? NULL in Indexes and Constraints: Considerations for NULL values extend to index structures and column constraints, impacting database integrity and performance.
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