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

Retrieving Multiple Columns

Let's explore this database a bit further. The country database consists of a single table named country. Let's examine the contents of this table.

This table has 15 rows, which means we have 15 distinct records for different countries.

Now, what about the columns? In this table, we have 7 columns, like id, name, continent, region, SurfaceArea, capital, and population.

id - the record number in this table;
name - the name of the country;
continent - the name of the country's continent;
region- the name of the country's region;
SurfaceArea - the total land area of the country;
capital - the capital of the country;
population - the population of the country.

We can also retrieve multiple columns with the SELECT operator. The only difference is that after the word SELECT, we will need to specify several column names, which must be separated by commas. Let’s take an example where we retrieve three columns from the country table:


              1
            
SELECT id, name, capital  FROM country;

Here's a short example of the country table:

Task

You need to retrieve the continent and population columns from the country table.

Task

You need to retrieve the continent and population columns from the country table.

Everything was clear?

Section 1. Chapter 2

Retrieving Multiple Columns

Let's explore this database a bit further. The country database consists of a single table named country. Let's examine the contents of this table.

This table has 15 rows, which means we have 15 distinct records for different countries.

Now, what about the columns? In this table, we have 7 columns, like id, name, continent, region, SurfaceArea, capital, and population.

id - the record number in this table;
name - the name of the country;
continent - the name of the country's continent;
region- the name of the country's region;
SurfaceArea - the total land area of the country;
capital - the capital of the country;
population - the population of the country.


              1
            
SELECT id, name, capital  FROM country;

Here's a short example of the country table:

Task

You need to retrieve the continent and population columns from the country table.

Task

You need to retrieve the continent and population columns from the country table.

Everything was clear?

Section 1. Chapter 2

Retrieving Multiple Columns

Let's explore this database a bit further. The country database consists of a single table named country. Let's examine the contents of this table.

This table has 15 rows, which means we have 15 distinct records for different countries.

Now, what about the columns? In this table, we have 7 columns, like id, name, continent, region, SurfaceArea, capital, and population.

id - the record number in this table;
name - the name of the country;
continent - the name of the country's continent;
region- the name of the country's region;
SurfaceArea - the total land area of the country;
capital - the capital of the country;
population - the population of the country.


              1
            
SELECT id, name, capital  FROM country;

Here's a short example of the country table:

Task

You need to retrieve the continent and population columns from the country table.

Task

You need to retrieve the continent and population columns from the country table.

Everything was clear?

Let's explore this database a bit further. The country database consists of a single table named country. Let's examine the contents of this table.

This table has 15 rows, which means we have 15 distinct records for different countries.

Now, what about the columns? In this table, we have 7 columns, like id, name, continent, region, SurfaceArea, capital, and population.

id - the record number in this table;
name - the name of the country;
continent - the name of the country's continent;
region- the name of the country's region;
SurfaceArea - the total land area of the country;
capital - the capital of the country;
population - the population of the country.


              1
            
SELECT id, name, capital  FROM country;

Here's a short example of the country table:

Task

You need to retrieve the continent and population columns from the country table.

Section 1. Chapter 2

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