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SQL | Aggregation and grouping exercise | Show continents/countries having lots of 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.
You can learn how to do this exercise if you attend one of more of the courses listed below!
- 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 a query listing out for each continent and country the number of events taking place therein:
The first few of the 42 rows you should get from this query, if you sort the results by country name.
You'll need to join the tblContinent, tblCountry and tblEvent tables. All good practice!
Now change your query so that it omits events taking place in the continent of Europe:
You should now be down to 25 rows.
Finally, change your query so that it only shows countries having 5 or more events:
You should now be down to 3 rows.
A thought: you should just have used every one of the SFWGHO letters!
Save your query as Post Brexit events, then close it down.
select max(con.ContinentName) as Continent_Name
, cou.CountryName as Country_Name
, count(e.EventName) as Number_of_Events
from [dbo].[tblEvent] e
left join [dbo].[tblCategory] c
on e.CategoryID = c.CategoryID
left join [dbo].[tblCountry] cou
on e.CountryID = cou.CountryID
left join [dbo].[tblContinent] con
on cou.ContinentID = con.ContinentID
where ContinentName not in('Europe')
group by cou.CountryName
having count(e.EventName) >= 5
order by cou.CountryName