Beginner

373. NULL vs Zero

Understand the important difference between NULL and zero.

📘 Lesson 373 of 728 ⏱ 9 min 🎯 Beginner

NULL represents a missing, unknown, or unavailable value, while zero is an actual numeric value representing 0.

Confusing NULL with zero can produce incorrect calculations, filters, and business reports.

A sales amount of 0 means no sales were recorded, while NULL may mean the sales amount is unknown or not provided.

SQL 
SELECT
    ProductName,
    SalesAmount
FROM Sales
WHERE SalesAmount IS NULL
   OR SalesAmount = 0;

Analysts must distinguish missing values from actual zero values when calculating KPIs, averages, totals, and business metrics.

  • NULL means missing or unknown.
  • Zero is an actual numeric value.
  • NULL and zero behave differently in calculations.
  • Use IS NULL to check NULL.
  • Use = 0 to check zero.
What is the difference between NULL and 0?

NULL represents a missing or unknown value, while 0 is an actual numeric value.

Can NULL be treated as zero automatically?

No. NULL requires explicit handling, often using functions such as COALESCE.

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