Summary  
This chapter covers how to filter records in SQL queries using the WHERE clause with comparison operators (equality, inequality, range checks, and NULL checks) to specify selection criteria.

General domain of usage  
Relational database querying

SQL supports a lot of conditional statements.



## Less Than

Let's look at the examples: <br>
This example lists all countries that have a population of **less than** 2424200:

SELECT name, population
FROM country
WHERE population < 2424200;

## Less Than or Equal to

The following example retrieves all countries with a population **less than or equal to** 2424200:

SELECT name, population
FROM country
WHERE population <= 2424200;

## Not Equal

The following example retrieves all non-Asian countries:


SELECT name, continent
FROM country
WHERE continent<>'Asia';

Which query returns the names of countries with a population equal to 2,424,200 using the '=' operator in the WHERE clause?

Which SQL query returns all countries that are not in Europe using the '<>' operator?

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 WHERE Clause Operators

Less Than

Less Than or Equal to

Not Equal

1. Which query returns the names of countries with a population equal to 2,424,200 using the '=' operator in the WHERE clause?

2. Which SQL query returns all countries that are not in Europe using the '<>' operator?

3. Write a SQL query to select the country name and population for all countries with a population between 5,000,000 and 50,000,000, inclusive. Use the BETWEEN operator.