COUNT

Returns the total number of rows in the table (includes NULL).

SELECT COUNT(*) FROM table_name;

Returns the number of rows where the specified column is not NULL.

SELECT COUNT(column_name) FROM table_name;

Returns the number of distinct (non-duplicate) values in the specified column.

SELECT COUNT(DISTINCT column_name) FROM table_name;

Returns the number of rows that match the condition.

SELECT COUNT(*) FROM table_name WHERE condition;

Syntax	Description
COUNT(*)	Counts all rows, including those with NULL values. This is the most common usage.
COUNT(column_name)	Counts only rows where the specified column is not NULL. Rows with NULL are excluded.
COUNT(DISTINCT column_name)	Counts the number of unique values in the specified column, excluding duplicates.

The following 'employees' table is used in the examples below.

Returns the total number of employees.

sample_count.sql

SELECT COUNT(*) AS employee_count FROM employees;

+----------------+
| employee_count |
+----------------+
|              5 |
+----------------+
1 row in set

Returns the number of employees who have a bonus set (excludes NULL).

sample_count.sql

SELECT COUNT(bonus) AS bonus_eligible_count FROM employees;

+----------------------+
| bonus_eligible_count |
+----------------------+
|                    3 |
+----------------------+
1 row in set

Returns the number of distinct departments.

sample_count.sql

SELECT COUNT(DISTINCT department) AS department_count FROM employees;

+------------------+
| department_count |
+------------------+
|                5 |
+------------------+
1 row in set

Returns the number of employees in the Dojima Family.

sample_count.sql

SELECT COUNT(*) AS dojima_count FROM employees WHERE department = 'Dojima Family';

+--------------+
| dojima_count |
+--------------+
|            1 |
+--------------+
1 row in set

Returns the number of employees per department (used with GROUP BY).

sample_count.sql

SELECT department, COUNT(*) AS headcount
FROM employees
GROUP BY department
ORDER BY headcount DESC;

+--------------------+-----------+
| department         | headcount |
+--------------------+-----------+
| Dojima Family      |         1 |
| Majima Family      |         1 |
| Sky Finance        |         1 |
| Nishikiyama Family |         1 |
| Saejima Family     |         1 |
+--------------------+-----------+
5 rows in set

The COUNT(*), COUNT(column_name), and COUNT(DISTINCT column_name) syntaxes work the same way across all major databases.

SELECT COUNT(*) AS employee_count FROM employees;
SELECT COUNT(DISTINCT department) AS department_count FROM employees;
SELECT department, COUNT(*) AS headcount FROM employees GROUP BY department;

COUNT is an aggregate function. The key difference between COUNT(*) and COUNT(column_name) is how they handle NULL values. If a column contains NULL values, the two forms can return different results on the same table, so use the appropriate form with care.

When using COUNT(*) > 0 to check whether rows exist, an EXISTS subquery is faster in MySQL because it stops as soon as a matching row is found. For existence checks on large tables, consider using EXISTS instead.

For per-group aggregation, see GROUP BY / HAVING. For totals and averages, see SUM / AVG.