What is the difference between the COUNT() function and the SUM() function in SQL?

Question

Aryan Kumar · Answer

In SQL, the COUNT and SUM functions serve different purposes and are used for different types of calculations.
COUNT Function:
The COUNT function is used to count the number of rows in a result set or the number of occurrences of a particular value in a column. It is often used in combination with the
GROUP BY clause to get counts for groups of data.
Syntax:
SELECT COUNT(column_name) FROM table_name WHERE condition;
If column_name is specified, it counts the number of non-NULL values in that column.If * is used instead of column_name, it counts the total number of rows in the result set.
Example:
-- Count the number of employees in the 'HR' department
SELECT COUNT(employee_id) FROM employees WHERE department = 'HR';
SUM Function:
The SUM function, on the other hand, is used to calculate the sum of numerical values in a column. It adds up the numeric values in the specified column.
Syntax:
SELECT SUM(column_name) FROM table_name WHERE condition;
It is applicable only to numeric columns.
Example:
-- Calculate the total salary of all employees
SELECT SUM(salary) FROM employees;
Key Differences:
Purpose:
COUNT is used to count the number of rows or occurrences.SUM is used to calculate the sum of numeric values.
Data Type:
COUNT can be used with any data type, including text and NULL values.SUM is specifically used with numeric data types.
Usage:
COUNT can be used without specifying a column (COUNT(*)) to count all rows, or with a specific column to count non-NULL values in that column.SUM is used with a specific numeric column to calculate the sum of its values.
NULL Handling:
COUNT counts the number of non-NULL values.SUM includes NULL values in the calculation, treating them as 0.
Example:
-- Count the number of employees and calculate the total salary
SELECT COUNT(employee_id) AS total_employees, SUM(salary) AS total_salary FROM employees;
In this example, we are using both COUNT and SUM to get the count of employees and the total salary in a single query.

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What is the difference between the COUNT() function and the SUM() function in SQL?

Revati S Misra

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1 Answers

COUNT Function:

SUM Function:

Key Differences:

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