Course Content

Introduction to SQL

1. Retrieving Data

Retrieving Individual Columns Retrieving Multiple Columns Retrieving All Columns Retrieving Distinct Rows Limiting Results Challenge: Find the Population of the Countries Challenge: Find All Countries Challenge: Find All Countries With Their IDs Challenge: Find Country Capitals Challenge: Find the Regions in Which All Countries Are Located

2. Sorting Retrieved Data

Sorting Data Challenge: Population Sort Sorting by Multiple Columns Challenge: Dual-Sort Query Specifying Sort Direction Challenge: Sort the Countries by Region and Capital Challenge: Sort Capitals in Descending Order Challenge: Sort Countries in Ascending Order Challenge: Find Countries, Their IDs, and Their Populations Challenge: Find Countries, IDs, Populations, Regions, and Sort Them Challenge: Find All Continents and Sort Them in Ascending Order

3. Filtering Data

Using the WHERE Clause Challenge: North America Population Sort The WHERE Clause Operators Challenge: Population Threshold Query Checking for a Range of Values Checking for NO Value

4. Advanced Data Filtering

Using the AND Operator Challenge: Europe Region Sort Using the OR operator Challenge: America Regions Filter Using the NOT Operator Challenge: Non-Europe Capitals Sort

5. Aggregate Functions

The AVG() Function Challenge: Surface Area Selection The COUNT() Function Challenge: Continental Count The MAX() Function The MIN() Function Challenge: Large Surface Area Average The SUM() Function

Specifying Sort Direction

Sorting Columns in Descending Order

We can do more than just sort data in ascending order by default. The ORDER BY clause can also arrange data in descending order, which requires using the DESC keyword.

Let's look at an example:


              123
            
SELECT continent 
FROM country 
ORDER BY continent DESC;

Sorting Multiple Columns in Descending Order

We can sort data by multiple columns, and in many cases, this is actually necessary. For example, when displaying a list of students, you might want to order them first by their last name and then by their first name. This approach is especially helpful when multiple students share the same name.

Also, if you’re sorting in descending order by more than one column, remember that each column must include its own DESC keyword.

Let's see an example.


              123
            
SELECT id, name, region 
FROM country 
ORDER BY region, name DESC;

Explanation: You only need to apply the DESC keyword to the column you want sorted in descending order. In our example, we used DESC for the name column but not for the region column. As a result, the name column is sorted in descending order, while the region column remains sorted in ascending order (the default).

Here is the country table we are working with:

Task

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Write an SQL query to retrieve five columns using the SELECT statement, namely: name, continent, region, population, and capital (please retrieve these columns in this order). Sort the result by two of them: first by continent in descending order, then by population in ascending order.

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Section 2. Chapter 5

Specifying Sort Direction

Sorting Columns in Descending Order

We can do more than just sort data in ascending order by default. The ORDER BY clause can also arrange data in descending order, which requires using the DESC keyword.

Let's look at an example:


              123
            
SELECT continent 
FROM country 
ORDER BY continent DESC;

Sorting Multiple Columns in Descending Order

Also, if you’re sorting in descending order by more than one column, remember that each column must include its own DESC keyword.

Let's see an example.


              123
            
SELECT id, name, region 
FROM country 
ORDER BY region, name DESC;

Here is the country table we are working with:

Task

Swipe to show code editor

Switch to desktop for real-world practiceContinue from where you are using one of the options below

Everything was clear?

Thanks for your feedback!

Section 2. Chapter 5

Specifying Sort Direction

Sorting Columns in Descending Order

We can do more than just sort data in ascending order by default. The ORDER BY clause can also arrange data in descending order, which requires using the DESC keyword.

Let's look at an example:


              123
            
SELECT continent 
FROM country 
ORDER BY continent DESC;

Sorting Multiple Columns in Descending Order

Also, if you’re sorting in descending order by more than one column, remember that each column must include its own DESC keyword.

Let's see an example.


              123
            
SELECT id, name, region 
FROM country 
ORDER BY region, name DESC;

Here is the country table we are working with:

Task

Swipe to show code editor

Switch to desktop for real-world practiceContinue from where you are using one of the options below

Everything was clear?

Thanks for your feedback!

Sorting Columns in Descending Order

We can do more than just sort data in ascending order by default. The ORDER BY clause can also arrange data in descending order, which requires using the DESC keyword.

Let's look at an example:


              123
            
SELECT continent 
FROM country 
ORDER BY continent DESC;

Sorting Multiple Columns in Descending Order

Also, if you’re sorting in descending order by more than one column, remember that each column must include its own DESC keyword.

Let's see an example.


              123
            
SELECT id, name, region 
FROM country 
ORDER BY region, name DESC;

Here is the country table we are working with:

Task

Swipe to show code editor

Switch to desktop for real-world practiceContinue from where you are using one of the options below

Section 2. Chapter 5

Switch to desktop for real-world practiceContinue from where you are using one of the options below