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Introduction to SQL
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Contenuti del Corso

Introduction to SQL

Introduction to SQL

1. Retrieving Data
Retrieving Individual ColumnsRetrieving Multiple Columns Retrieving All ColumnsRetrieving Distinct RowsLimiting ResultsChallenge: Find the Population of the CountriesChallenge: Find All CountriesChallenge: Find All Countries With Their IDsChallenge: Find Country CapitalsChallenge: Find the Regions in Which All Countries Are Located
2. Sorting Retrieved Data
Sorting DataChallenge: Population SortSorting by Multiple ColumnsChallenge: Dual-Sort QuerySpecifying Sort DirectionChallenge: Sort the Countries by Region and CapitalChallenge: Sort Capitals in Descending OrderChallenge: Sort Countries in Ascending OrderChallenge: Find Countries, Their IDs, and Their PopulationsChallenge: Find Countries, IDs, Populations, Regions, and Sort ThemChallenge: Find All Continents and Sort Them in Ascending Order
3. Filtering Data
Using the WHERE ClauseChallenge: North America Population SortThe WHERE Clause Operators Challenge: Population Threshold QueryChecking for a Range of ValuesChecking for NO Value
4. Advanced Data Filtering
Using the AND OperatorChallenge: Europe Region SortUsing the OR operatorChallenge: America Regions FilterUsing the NOT OperatorChallenge: Non-Europe Capitals Sort
5. Aggregate Functions
The AVG() FunctionChallenge: Surface Area SelectionThe COUNT() FunctionChallenge: Continental CountThe MAX() FunctionThe MIN() FunctionChallenge: Large Surface Area AverageThe SUM() Function

book
Checking for NO Value

If a column doesn't contain any data, it's considered NULL. To determine if a value is NULL, you don’t just check for equality. Instead, you use the WHERE clause with IS NULL in a SELECT statement to find rows where the column’s value is NULL.

The syntax for it looks like this:

sql

Let's illustrate this with an example:


              
123

            
SELECT name
FROM country
WHERE region IS NULL;
copy

Here is the country table we are working with:

Compito

Swipe to start coding

Write an SQL query that returns the name and capital columns with no population.

Soluzione

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Tutto è chiaro?

Come possiamo migliorarlo?

Grazie per i tuoi commenti!

Sezione 3. Capitolo 6
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book
Checking for NO Value

If a column doesn't contain any data, it's considered NULL. To determine if a value is NULL, you don’t just check for equality. Instead, you use the WHERE clause with IS NULL in a SELECT statement to find rows where the column’s value is NULL.

The syntax for it looks like this:

sql

Let's illustrate this with an example:


              
123

            
SELECT name
FROM country
WHERE region IS NULL;
copy

Here is the country table we are working with:

Compito

Swipe to start coding

Write an SQL query that returns the name and capital columns with no population.

Soluzione

Switch to desktopCambia al desktop per esercitarti nel mondo realeContinua da dove ti trovi utilizzando una delle opzioni seguenti
Tutto è chiaro?

Come possiamo migliorarlo?

Grazie per i tuoi commenti!

Sezione 3. Capitolo 6
Switch to desktopCambia al desktop per esercitarti nel mondo realeContinua da dove ti trovi utilizzando una delle opzioni seguenti
Siamo spiacenti che qualcosa sia andato storto. Cosa è successo?
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