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Software ==>	SQL (203 exercises)
Topic ==>	Derived tables and CTEs (19 exercises)
Level ==>	Harder than average
Subject ==>	SQL training

For each combination of the top 3 categories and top 3 countries, count the number of events using CTEs

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).

Create two CTEs in the same query as follows:

CTE	What it should list out
TopCountries	The ids of the 3 countries with the most events (use TOP 3)
TopCategories	The ids of the 3 categories with the most events (use TOP 3 again)

Use these to show all possible combinations in a final SELECT statement which should look like this:

-- combine these together (every possible combination)

SELECT

cy.CountryID,

cg.CategoryID

FROM

TopCountries AS cy

CROSS JOIN TopCategories AS cg

The cross join gives all possible combinations of rows in the two CTEs - see below for what the results should look like.

You should now be looking at something like this:

There are 9 possible combinations.

If you still have the energy, use this to show the number of events for each combination:

United Kingdom / Politics is the combination of country and category which has the most events.

Save this as Country category combinations, 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:

This page has 1 thread

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From:	Zeshan Tahir
When:	06 Oct 17 at 10:51

Hi!

I have completed the main task but i cannot be able to append the NumberofEvents column - please help me with this.

From:	Andy B
When:	06 Oct 17 at 11:58

We don't give out additional technical help, but maybe some kind reader would oblige?

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EXERCISE TOPIC

SQL EXERCISES

SQL EXERCISES

For each combination of the top 3 categories and top 3 countries, count the number of events using CTEs

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