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Using the WHERE Clause | Filtering Data
Introduction to SQL
course content

Course Content

Introduction to SQL

Introduction to SQL

1. Retrieving Data
2. Sorting Retrieved Data
3. Filtering Data
4. Advanced Data Filtering
5. Aggregate Functions

bookUsing the WHERE Clause

In databases, tables typically hold substantial volumes of data. However, frequently we're interested in retrieving specific portions of the data rather than the entirety. To accomplish this, we need to define the conditions for data retrieval, which are referred to as filtering criteria.

Data is filtered using a WHERE clause specifying the search criteria in a SELECT statement. The WHERE clause appears immediately after the table name.

Let's see an example:

123
SELECT name, continent FROM country WHERE continent='Europe';
copy

Explanation: The SELECT statement gets 2 columns from the country table and returns only rows with the continent value 'Europe'.

Note

Note that we need to enclose the value in single quotation marks('').

Clause Position

When we use the ORDER BY and WHERE clauses, we ensure the ORDER BY comes after the WHERE clause. Let's see the following example:

1234
SELECT capital, continent FROM country WHERE continent='Asia' ORDER BY continent DESC;
copy

Task

Write an SQL query to retrieve the id, name, and region columns from the country table (please retrieve these columns in this order), returning only rows with the 'North America' continent.

Please note that North America should be correctly capitalized, and north america is not the same. So, be careful and write it as North America.

Here's a short example of the country table:

idnamecontinentregionsurfaceareacapitalpopulation
1JapanAsiaEastern Asia377829Tokyo126714000
2LatviaEuropeNULL64589Riga2424200
3MexicoNorth AmericaCentral America1958201Mexico City98881000
.....................
15MaltaEuropeSouthern Europe316Valletta380200

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Section 3. Chapter 1
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bookUsing the WHERE Clause

In databases, tables typically hold substantial volumes of data. However, frequently we're interested in retrieving specific portions of the data rather than the entirety. To accomplish this, we need to define the conditions for data retrieval, which are referred to as filtering criteria.

Data is filtered using a WHERE clause specifying the search criteria in a SELECT statement. The WHERE clause appears immediately after the table name.

Let's see an example:

123
SELECT name, continent FROM country WHERE continent='Europe';
copy

Explanation: The SELECT statement gets 2 columns from the country table and returns only rows with the continent value 'Europe'.

Note

Note that we need to enclose the value in single quotation marks('').

Clause Position

When we use the ORDER BY and WHERE clauses, we ensure the ORDER BY comes after the WHERE clause. Let's see the following example:

1234
SELECT capital, continent FROM country WHERE continent='Asia' ORDER BY continent DESC;
copy

Task

Write an SQL query to retrieve the id, name, and region columns from the country table (please retrieve these columns in this order), returning only rows with the 'North America' continent.

Please note that North America should be correctly capitalized, and north america is not the same. So, be careful and write it as North America.

Here's a short example of the country table:

idnamecontinentregionsurfaceareacapitalpopulation
1JapanAsiaEastern Asia377829Tokyo126714000
2LatviaEuropeNULL64589Riga2424200
3MexicoNorth AmericaCentral America1958201Mexico City98881000
.....................
15MaltaEuropeSouthern Europe316Valletta380200

Switch to desktopSwitch to desktop for real-world practiceContinue from where you are using one of the options below
Everything was clear?

How can we improve it?

Thanks for your feedback!

Section 3. Chapter 1
toggle bottom row

bookUsing the WHERE Clause

In databases, tables typically hold substantial volumes of data. However, frequently we're interested in retrieving specific portions of the data rather than the entirety. To accomplish this, we need to define the conditions for data retrieval, which are referred to as filtering criteria.

Data is filtered using a WHERE clause specifying the search criteria in a SELECT statement. The WHERE clause appears immediately after the table name.

Let's see an example:

123
SELECT name, continent FROM country WHERE continent='Europe';
copy

Explanation: The SELECT statement gets 2 columns from the country table and returns only rows with the continent value 'Europe'.

Note

Note that we need to enclose the value in single quotation marks('').

Clause Position

When we use the ORDER BY and WHERE clauses, we ensure the ORDER BY comes after the WHERE clause. Let's see the following example:

1234
SELECT capital, continent FROM country WHERE continent='Asia' ORDER BY continent DESC;
copy

Task

Write an SQL query to retrieve the id, name, and region columns from the country table (please retrieve these columns in this order), returning only rows with the 'North America' continent.

Please note that North America should be correctly capitalized, and north america is not the same. So, be careful and write it as North America.

Here's a short example of the country table:

idnamecontinentregionsurfaceareacapitalpopulation
1JapanAsiaEastern Asia377829Tokyo126714000
2LatviaEuropeNULL64589Riga2424200
3MexicoNorth AmericaCentral America1958201Mexico City98881000
.....................
15MaltaEuropeSouthern Europe316Valletta380200

Switch to desktopSwitch to desktop for real-world practiceContinue from where you are using one of the options below
Everything was clear?

How can we improve it?

Thanks for your feedback!

In databases, tables typically hold substantial volumes of data. However, frequently we're interested in retrieving specific portions of the data rather than the entirety. To accomplish this, we need to define the conditions for data retrieval, which are referred to as filtering criteria.

Data is filtered using a WHERE clause specifying the search criteria in a SELECT statement. The WHERE clause appears immediately after the table name.

Let's see an example:

123
SELECT name, continent FROM country WHERE continent='Europe';
copy

Explanation: The SELECT statement gets 2 columns from the country table and returns only rows with the continent value 'Europe'.

Note

Note that we need to enclose the value in single quotation marks('').

Clause Position

When we use the ORDER BY and WHERE clauses, we ensure the ORDER BY comes after the WHERE clause. Let's see the following example:

1234
SELECT capital, continent FROM country WHERE continent='Asia' ORDER BY continent DESC;
copy

Task

Write an SQL query to retrieve the id, name, and region columns from the country table (please retrieve these columns in this order), returning only rows with the 'North America' continent.

Please note that North America should be correctly capitalized, and north america is not the same. So, be careful and write it as North America.

Here's a short example of the country table:

idnamecontinentregionsurfaceareacapitalpopulation
1JapanAsiaEastern Asia377829Tokyo126714000
2LatviaEuropeNULL64589Riga2424200
3MexicoNorth AmericaCentral America1958201Mexico City98881000
.....................
15MaltaEuropeSouthern Europe316Valletta380200

Switch to desktopSwitch to desktop for real-world practiceContinue from where you are using one of the options below
Section 3. Chapter 1
Switch to desktopSwitch to desktop for real-world practiceContinue from where you are using one of the options below
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