Beginner

84. NULL with COUNT

Understand how NULL values affect COUNT(*) and COUNT(column).

📘 Lesson 84 of 728 ⏱ 8 min 🎯 Beginner

COUNT(*) counts all rows, including rows containing NULL values. COUNT(column_name) counts only non-NULL values in the specified column.

Knowing how COUNT handles NULL values prevents incorrect reporting and helps analysts measure both total records and available values.

If a table contains 100 employees but 10 employees have no email address, COUNT(*) returns 100 while COUNT(Email) returns 90.

SQL 
SELECT
    COUNT(*) AS TotalEmployees,
    COUNT(Email) AS EmployeesWithEmail
FROM Employees;

This is useful for data completeness analysis, customer contact validation, employee records, and data-quality reporting.

  • COUNT(*) counts every row.
  • COUNT(column) ignores NULL values.
  • COUNT(*) and COUNT(column) can return different results.
  • This behavior is important for data-quality analysis.
  • COUNT can measure data completeness.
Does COUNT(*) count rows containing NULL?

Yes. COUNT(*) counts every row regardless of NULL values.

Does COUNT(column) count NULL values?

No. COUNT(column) counts only non-NULL values.

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