T-SQL SUM() Function

The T-SQL (Transact-SQL) SUM() function returns the summed value of an expression.

Syntax

The syntax for using SUM() function is given below:

SELECT SUM(column_name) 
FROM table_name
WHERE condition(s);

The T-SQL (Transact-SQL) GROUP BY clause is used to arrange result table into identical groups when one or more columns are used. Please note that it is must to include those column names in a GROUP BY clause which are not encapsulated within the SUM() function. See the syntax below:

SELECT column1, column2, ...
       SUM(column_name) 
FROM table_name
WHERE condition(s)
GROUP BY column1, column2, ...;

Parameters

Return Value

Returns the summed value of a given expression.

Example - With Single Column

Consider a database table called Employee with the following records:

To get the combined total salary of all employees whose age is greater than 25, the following query can be used:

SELECT SUM(Salary) AS TotalSalary 
FROM Employee
WHERE Age > 25;

This will produce the result as shown below:

Example - Using DISTINCT

The DISTICT clause can be used with SUM() function. For example - To get the combined total salary of distinct (unique) salaries, the following code can be used:

SELECT SUM(DISTINCT Salary) AS TotalUniqueSalary 
FROM Employee;

This will produce the result as shown below:

Example - Using Formula

The expression contained within the SUM() function does not need to be a single field. A formula can also be used with this function. For example - Consider a bonus (15% of Salary) is given to each employee, and to calculate the total bonus amount, the following query can be used:

SELECT SUM(Salary * 0.15) AS TotalBonusAmount
FROM Employee;

This will produce the result as shown below:

Example - Using GROUP BY

To get the combined total salary of employees group by their age, the following query can be used:

SELECT Age, SUM(Salary) AS TotalSalaryByAge 
FROM Employee
GROUP BY Age;

This result of the above code will be: