Extra challenges (optional)

Overview

Questions

• Are there extra challenges to practice translating plain English queries to SQL queries?

Objectives

• Extra challenges to practice creating SQL queries.

Extra challenges (optional)

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SQL queries help us ask specific questions which we want to answer about our data. The real skill with SQL is to know how to translate our questions into a sensible SQL queries (and subsequently visualise and interpret our results).

Have a look at the following questions; these questions are written in plain English. Can you translate them to SQL queries and give a suitable answer?

Also, if you would like to learn more SQL concepts and try additional challenges, see the Software Carpentry Databases and SQL lesson.

Challenge 1

How many articles are there from each First_author? Can you make an alias for the number of articles? Can you order the results by articles?

Solution 1

SQL

SELECT First_Author, COUNT( * ) AS n_articles
FROM articles
GROUP BY First_Author
ORDER BY n_articles DESC;

Challenge 2

How many papers have a single author? How many have 2 authors? How many 3? etc?

Solution 2

SQL

SELECT Author_Count, COUNT( * )
FROM articles
GROUP BY Author_Count;

Challenge 3

How many articles are published for each Language? Ignore articles where language is unknown.

Solution 3

SQL

SELECT Language, COUNT( * )
FROM articles
JOIN languages
ON articles.LanguageId=languages.id
WHERE Language != ''
GROUP BY Language;

Challenge 4

How many articles are published for each Licence type, and what is the average number of citations for that Licence type?

Solution 4

SQL

SELECT Licence, AVG( Citation_Count ), COUNT( * )
FROM articles
JOIN licences
ON articles.LicenceId=licences.id
WHERE Licence != ''
GROUP BY Licence;

Challenge 5

Write a query that returns Title, First_Author, Author_Count, Citation_Count, Month, Year, Journal_Title and Publisher for articles in the database.

Solution 5

SQL

SELECT Title, First_Author, Author_Count, Citation_Count, Month, Year, Journal_Title, Publisher
FROM articles
JOIN journals
ON articles.issns=journals.ISSNs
JOIN publishers
ON publishers.id=journals.PublisherId;

Keypoints

• It takes time and practice to learn how to translate plain English queries into SQL queries.