Kursinnehåll

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 Multiple Columns

Inspecting the Table

Let's delve deeper into the country database. This database contains a single table, also named country. We'll take a closer look at the data within this table.

This table contains 15 rows, representing 15 unique records for various countries.

Now, let's discuss the columns. The table includes 7 columns: id, name, continent, region, SurfaceArea, capital, and population.

id - the unique identifier for each record;
name - the name of the country;
continent - the continent where the country is located;
region - the specific region within the continent;
SurfaceArea - the total land area of the country;
capital - the capital city of the country;
population - the number of people living in the country.

The Syntax for Selecting Multiple Columns

To retrieve multiple columns, use the SELECT statement. After SELECT, list the column names you want to retrieve, separated by commas.

The syntax looks like this:

sql

Here's an example of how to select three columns from the country table:


              12
            
SELECT id, name, capital 
FROM country;

Here's a short example of the country table:

Uppgift

Swipe to start coding

Write an SQL query to retrieve the continent and population columns from the country table.

Note

Remember that columns must be separated by commas!

Lösning

Byt till skrivbordet för praktisk övningFortsätt där du är med ett av alternativen nedan

Var allt tydligt?

Tack för dina kommentarer!

Avsnitt 1. Kapitel 2

Retrieving Multiple Columns

Inspecting the Table

Let's delve deeper into the country database. This database contains a single table, also named country. We'll take a closer look at the data within this table.

This table contains 15 rows, representing 15 unique records for various countries.

Now, let's discuss the columns. The table includes 7 columns: id, name, continent, region, SurfaceArea, capital, and population.

id - the unique identifier for each record;
name - the name of the country;
continent - the continent where the country is located;
region - the specific region within the continent;
SurfaceArea - the total land area of the country;
capital - the capital city of the country;
population - the number of people living in the country.

The Syntax for Selecting Multiple Columns

To retrieve multiple columns, use the SELECT statement. After SELECT, list the column names you want to retrieve, separated by commas.

The syntax looks like this:

sql

Here's an example of how to select three columns from the country table:


              12
            
SELECT id, name, capital 
FROM country;

Here's a short example of the country table:

Uppgift

Swipe to start coding

Write an SQL query to retrieve the continent and population columns from the country table.

Note

Remember that columns must be separated by commas!

Lösning

Byt till skrivbordet för praktisk övningFortsätt där du är med ett av alternativen nedan

Var allt tydligt?

Tack för dina kommentarer!

Avsnitt 1. Kapitel 2

Byt till skrivbordet för praktisk övningFortsätt där du är med ett av alternativen nedan