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SQL | Derived tables and CTEs exercise | Show the number of events for the top 3 categories/countries
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.
- 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).
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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)
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.
I have completed the main task but i cannot be able to append the NumberofEvents column - please help me with this.