Summary  
This chapter explains how to use the SQL AVG() aggregate function to compute the mean value of a column, both across all rows and on a subset defined by a WHERE condition.  

General domain of usage  
Relational database querying and data analysis

`AVG()` returns the average value of a certain column. 
Let's see an example: 

`AVG()` can also be used to find the average of a selected set of columns or rows that meet certain conditions. Here’s an example:

SELECT AVG(population) 
FROM country
WHERE population < 4478500;

What does the `AVG()` function return in SQL?

Which SQL clause can be used with `AVG()` to calculate the average for a subset of rows?

This course is perfect for beginners ready to explore the world of SQL. Whether you're just starting out in database management or aiming to use SQL for your application development projects, this course covers the essentials. You'll quickly learn how to leverage the full potential of SQL, from querying and managing data to seamlessly integrating it into real-world applications. By the end of the course, you'll have the confidence and skills to solve practical problems with SQL and enhance your development process.

In this section, we will learn how to use the SQL SELECT statement to get a single table column, multiple table columns, and all table columns. We will also find out how to return unique values.

In this section, we’ll explore how to organize and prioritize the data returned by a query using the ORDER BY clause. Placed at the end of a SELECT statement, this clause lets you sort your results by one or multiple columns, either in ascending or descending order, enabling more meaningful and easily interpretable data output.

In this section, we will learn how to filter returned data using the SELECT statement's WHERE clause. We will learn how to test for equality, inequality, more and less significant than value ranges, and NULL values.

In this section, we’ll explore how to refine your search conditions by combining WHERE clauses with the AND and OR operators. We’ll also cover how the NOT operator can be used to exclude certain results.

In this section, we will learn what the SQL aggregate functions are and how to use them to summarize table data.

The AVG() Function

1. What does the `AVG()` function return in SQL?

2. Which SQL clause can be used with `AVG()` to calculate the average for a subset of rows?

The AVG() Function

1. What does the `AVG()` function return in SQL?

2. Which SQL clause can be used with `AVG()` to calculate the average for a subset of rows?

The AVG() Function

1. What does the AVG() function return in SQL?

2. Which SQL clause can be used with AVG() to calculate the average for a subset of rows?

The AVG() Function

1. What does the AVG() function return in SQL?

2. Which SQL clause can be used with AVG() to calculate the average for a subset of rows?

1. What does the `AVG()` function return in SQL?

2. Which SQL clause can be used with `AVG()` to calculate the average for a subset of rows?

1. What does the `AVG()` function return in SQL?

2. Which SQL clause can be used with `AVG()` to calculate the average for a subset of rows?