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Software ==>	SQL (129 exercises)
Topic ==>	Derived tables and CTEs (13 exercises)
Level ==>	Average difficulty
Subject ==>	SQL training

Use linked CTEs to show continents having many countries but few events

This exercise is provided to allow potential course delegates to choose the correct Wise Owl Microsoft training course, and may not be reproduced in whole or in part in any format without the prior written consent of Wise Owl.

Before you can do this exercise, you'll need to download and unzip this file. Once you've done this:

Go into SQL Server Management Studio;
Open the SQL file you've just unzipped (you can press CTRL + O to do this); then
Execute this script.

This will generate the database that you'll need to use in order to do this exercise (note that the database and script are only to be used for exercises published on this website, and may not be reused or distributed in any form without the prior written permission of Wise Owl).

The aim of this exercise is to list out all the continents which have:

At least 3 countries; but also
At most 10 events.

It's worth noting that there are many ways to solve this in SQL, but as is so often the case CTEs seem to give the most intuitive approach.

To do this, all that you need to do is to create the following CTEs:

CTE	What it should contain
ManyCountries	A list of continents having at least 3 countries
FewEvents	A list of continents in which no more than 10 events occurred

You can then join them together to show that there is only one country in both camps. We won't spoil the surprise, but it has (in the Wise Owl database, at any rate) 4 countries and 9 events.

Optionally, save this as Toto.sql, then close it down.

You can unzip this file to see the answers to this exercise, although please remember this is for your personal use only.

You can find other training resources for the subject of this exercise here:

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