Extra challenges (optional)

Objectives

Extra challenges to practice creating SQL queries.

Questions

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

Extra challenges (optional)

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

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

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

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

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

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.