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Aggregate Functions In SQL Server

     In SQL Server, aggregate functions are used to perform calculations on a set of values and return a single value. These functions operate on multiple rows of a table and return a single value based on the specified criteria. In this blog, we will discuss the aggregate functions available in SQL Server.

COUNT Function:

The COUNT function returns the number of rows that match the specified criteria. It can be used with the asterisk (*) wildcard to count all rows in a table.

Syntax:

COUNT(* | [ALL|DISTINCT] expression)

Example:

SELECT COUNT(*) AS TotalEmployees FROM Employees

In this example, the COUNT function is used to count the total number of rows in the Employees table.

SUM Function:

The SUM function returns the sum of all values in a column.

Syntax:

SUM([ALL|DISTINCT] expression)

Example:

SELECT SUM(Salary) AS TotalSalary FROM Employees

In this example, the SUM function is used to calculate the total salary of all employees in the Employees table.

AVG Function:

The AVG function returns the average value of a column.

Syntax:

AVG([ALL|DISTINCT] expression)

Example:

SELECT AVG(Salary) AS AverageSalary FROM Employees

In this example, the AVG function is used to calculate the average salary of all employees in the Employees table.

MIN Function:

The MIN function returns the minimum value in a column.

Syntax:

MIN([ALL|DISTINCT] expression)

Example:

SELECT MIN(Salary) AS MinimumSalary FROM Employees

In this example, the MIN function is used to find the minimum salary of all employees in the Employees table.

MAX Function:

The MAX function returns the maximum value in a column.

Syntax:

MAX([ALL|DISTINCT] expression)

Example:

SELECT MAX(Salary) AS MaximumSalary FROM Employees

In this example, the MAX function is used to find the maximum salary of all employees in the Employees table.

GROUP BY Function:

The GROUP BY function is used to group rows with the same values in a column and perform aggregate functions on each group.

Syntax:

SELECT column_name, aggregate_function(column_name)

FROM table_name

GROUP BY column_name;

 

Example:

SELECT Department, SUM(Salary) AS TotalSalary FROM Employees

GROUP BY Department

In this example, the GROUP BY function is used to group employees by department and calculate the total salary of each department.

HAVING Function:

The HAVING function is used with the GROUP BY function to filter groups based on specific criteria.

Syntax:

SELECT column_name, aggregate_function(column_name)

FROM table_name

GROUP BY column_name

HAVING aggregate_function(column_name) operator value;

 

Example:

SELECT Department, SUM(Salary) AS TotalSalary FROM Employees

GROUP BY Department

HAVING SUM(Salary) > 100000

 

In this example, the HAVING function is used to filter departments whose total salary is greater than 100000.

Conclusion:

In SQL Server, aggregate functions are used to perform calculations on a set of values and return a single value. The most commonly used aggregate functions are COUNT, SUM, AVG, MIN, and MAX. The GROUP BY and HAVING functions are used to group and filter rows based on specific criteria. By using these functions, we can easily summarize data and perform complex calculations on large sets of data in SQL Server.

Reference

              https://learn.microsoft.com/en-us/sql/t-sql/functions/aggregate-functions-transact-sql?view=sql-server-ver16


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