Introduction to SQL

Introduction to SQL

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1. Retrieving Data

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.

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

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.

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

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.

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

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.

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

In this section, we will learn what the SQL aggregate functions are and how to use them to summarize table data.

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

Course Content

Introduction to SQL

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 All Columns

Instead of listing each column, you can use the asterisk * to retrieve all columns from the table at once. This is especially useful when you need to view all the data in a table without manually typing out each column name. Here’s an example:


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SELECT * 
FROM table_name;

Task

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Write an SQL query to retrieve ALL columns from the country table.

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Section 1. Chapter 3

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Retrieving All Columns

Instead of listing each column, you can use the asterisk * to retrieve all columns from the table at once. This is especially useful when you need to view all the data in a table without manually typing out each column name. Here’s an example:


              12
            
SELECT * 
FROM table_name;

Task

Swipe to show code editor

Write an SQL query to retrieve ALL columns 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 3

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

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