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

Retrieving Distinct Rows

Note that the SELECT statement returns all rows in a given column. However, what if we don't need all the values from a column, especially when they are duplicated, and we only need unique values?

For such cases, it is convenient to use the keyword DISTINCT, placed immediately before the column names. Let's take a look at an example:


              12
            
SELECT DISTINCT region 
FROM country;

Here's a short example of the country table:

Task

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Write an SQL query to retrieve distinct (unique) continent values from the country table.

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

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Thanks for your feedback!

Section 1. Chapter 4

Retrieving Distinct Rows

For such cases, it is convenient to use the keyword DISTINCT, placed immediately before the column names. Let's take a look at an example:


              12
            
SELECT DISTINCT region 
FROM country;

Here's a short example of the country table:

Task

Swipe to show code editor

Write an SQL query to retrieve distinct (unique) continent values from the country table.

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 1. Chapter 4

Retrieving Distinct Rows

For such cases, it is convenient to use the keyword DISTINCT, placed immediately before the column names. Let's take a look at an example:


              12
            
SELECT DISTINCT region 
FROM country;

Here's a short example of the country table:

Task

Swipe to show code editor

Write an SQL query to retrieve distinct (unique) continent values from the country table.

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

Everything was clear?

Thanks for your feedback!

For such cases, it is convenient to use the keyword DISTINCT, placed immediately before the column names. Let's take a look at an example:


              12
            
SELECT DISTINCT region 
FROM country;

Here's a short example of the country table:

Task

Swipe to show code editor

Write an SQL query to retrieve distinct (unique) continent values from the country table.

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

Section 1. Chapter 4

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