Beginner

188. NULL vs Empty String

Understand the difference between NULL and an empty text value.

📘 Lesson 188 of 728 ⏱ 9 min 🎯 Beginner

NULL represents missing or unknown information, while an empty string represents a text value containing zero characters. Their behavior can differ between database systems and data types.

Correctly distinguishing missing values from intentionally empty text is important for data-quality analysis.

A customer's middle name may be NULL when it is unknown, while an empty string may indicate that the field was intentionally left blank.

SQL 
SELECT
    CustomerName,
    Email
FROM Customers
WHERE Email IS NULL
   OR Email = '';

This distinction matters in customer databases, employee records, data cleansing, application systems, and reporting.

  • NULL represents missing or unknown information.
  • An empty string contains zero text characters.
  • They are not automatically equivalent.
  • Database behavior can vary.
  • Both may need separate handling during data cleaning.
Is NULL the same as an empty string?

No. NULL represents missing or unknown information, while an empty string is a text value containing no characters.

Why check NULL and empty strings separately?

Because they represent different states and may require different handling in data-quality processes.

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