Summary  
This chapter covers using conditional filtering with the WHERE clause and applying aggregate functions (COUNT, SUM, AVG, MIN, MAX) to compute summary statistics on datasets.

General domain of usage  
Data analysis

## Summary

In the last part of the course, you explored two essential SQL skills: **filtering data** and using **aggregate functions**. Mastering these topics is crucial for analyzing and summarizing information stored in databases.

- Filtering data: use the `WHERE` clause to retrieve only the rows that meet specific conditions; this helps you focus on relevant information and answer precise business questions;
- Aggregate functions: apply functions like `COUNT`, `SUM`, `AVG`, `MIN`, and `MAX` to calculate totals, averages, and other summary statistics; these are valuable for producing reports and insights from large datasets.

You typically use filtering and aggregate functions together to generate meaningful summaries, such as finding the average population for countries in a specific region or identifying the largest country by surface area. These skills are fundamental for anyone working with data in SQL.

Which clause is used to filter rows in a SQL SELECT statement before any grouping or aggregation?

Which of the following is an aggregate function in SQL?

Which aggregate function returns the average value of a numeric column in SQL?

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.

Course Summary

Summary

1. Which clause is used to filter rows in a SQL SELECT statement before any grouping or aggregation?

2. Which of the following is an aggregate function in SQL?

3. Write a SQL query to find the total population of countries in Asia using the SUM aggregate function. Only include countries where the continent is Asia.

4. Write a SQL query to find out how many countries have a population greater than 10 million. Use the COUNT aggregate function and the WHERE clause.

5. Which aggregate function returns the average value of a numeric column in SQL?