SQL for Data Analysis

This is a very well put together introduction to SQL, using one consistent toy data example throughout (the database of orders and accounts for a fictional paper company). New features of SQL are introduced at a sensible pace, and there are frequent quizzes which ask you to create your own queries to interact with the database.

Unlike some other online courses, I didn't feel at any point that I was being left to go read all the online documentation for something on my own, as it wasn't explained properly. Neither did I feel that I was only being asked to construct trivial queries that wouldn't actually develop my understanding.

Here's an example problem set, from the GROUP BY section of the third chapter:

1. For each account, determine the average amount of each type of paper they purchased across their orders. Your result should have four columns - one for the account name and one for the average quantity purchased for each of the paper types for each account.

2. For each account, determine the average amount spent per order on each paper type. Your result should have four columns - one for the account name and one for the average amount spent on each paper type.

3. Determine the number of times a particular channel was used in the web_events table for each sales rep. Your final table should have three columns - the name of the sales rep, the channel, and the number of occurrences. Order your table with the highest number of occurrences first.

4. Determine the number of times a particular channel was used in the web_events table for each region. Your final table should have three columns - the region name, the channel, and the number of occurrences. Order your table with the highest number of occurrences first.