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home / developersection / interviews / difference between count(*) vs count(column).
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Ravi Vishwakarma
Ravi Vishwakarma

IT-Hardware & Networking

Ravi Vishwakarma is a dedicated Software Developer with a passion for crafting efficient and innovative solutions. With a keen eye for detail and years of experience, he excels in developing robust software systems that meet client needs. His expertise spans across multiple programming languages and technologies, making him a valuable asset in any software development project.

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1 Answers

Ravi Vishwakarma
Ravi Vishwakarma 08 May 2026
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In SQL, both COUNT(*) and COUNT(column) count rows, but they behave differently with NULL values.

COUNT(*)

Counts all rows in the result set, including rows where columns contain NULL.

Example:

SELECT COUNT(*) FROM employees;

If the table has 10 rows, result = 10.

COUNT(column)

Counts only rows where the specified column is NOT NULL.

Example:

SELECT COUNT(email) FROM employees;

If email has:

id email
1 a@example.com
2 NULL
3 b@example.com

Then:

COUNT(email) = 2
COUNT(*) = 3

Key Difference

Function Counts NULLs? What it counts
COUNT(*) Yes All rows
COUNT(column) No Non-NULL values in that column

With GROUP BY

Example:

SELECT department_id, COUNT(*), COUNT(manager_id)
FROM employees
GROUP BY department_id;
  • COUNT(*) → total employees in each department
  • COUNT(manager_id) → employees whose manager_id is not NULL

Performance Notes

In modern databases (like PostgreSQL, MySQL, SQL Server, Oracle):

  • COUNT(*) is usually optimized and preferred for counting rows.
  • COUNT(1) and COUNT(*) are generally equivalent in performance.
  • COUNT(column) may behave differently because it must check for NULLs.

Quick Rule

Use:

  • COUNT(*) → when you want total row count
  • COUNT(column) → when you want count of non-null values in a specific column        
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