SQL > Aggregate Functions

Introduction

Aggregate functions in SQL perform calculations on multiple rows of data and return a single result. These functions are commonly used with the GROUP BY clause to summarize data.

Key Aggregate Functions:

1. COUNT - Returns the number of rows.
2. SUM - Calculates the total sum of a numeric column.
3. AVG - Returns the average value of a numeric column.
4. MIN - Retrieves the minimum value.
5. MAX - Retrieves the maximum value.

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1. COUNT Function

Purpose:

The COUNT function returns the number of rows in a table or the number of non-null values in a column.

Syntax:

SELECT COUNT(column_name) FROM table_name;

Example:

SELECT COUNT(OrderID) FROM Orders;

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2. SUM Function

Purpose:

The SUM function calculates the total sum of a numeric column.

Syntax:

SELECT SUM(column_name) FROM table_name;

Example:

SELECT SUM(TotalAmount) FROM Orders;

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3. AVG Function

Purpose:

The AVG function calculates the average value of a numeric column.

Syntax:

SELECT AVG(column_name) FROM table_name;

Example:

SELECT AVG(Grade) FROM Students;

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4. MIN Function

Purpose:

The MIN function retrieves the lowest value in a column.

Syntax:

SELECT MIN(column_name) FROM table_name;

Example:

SELECT MIN(Salary) FROM Employees;

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5. MAX Function

Purpose:

The MAX function retrieves the highest value in a column.

Syntax:

SELECT MAX(column_name) FROM table_name;

Example:

SELECT MAX(Price) FROM Products;

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Summary

Function	Description
COUNT	Returns the number of rows.
SUM	Calculates the total sum of a numeric column.
AVG	Returns the average value of a numeric column.
MIN	Retrieves the minimum value.
MAX	Retrieves the maximum value.

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