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SQL | Calculations exercise | Show how big countries are in relation to Wales
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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First open the script in the folder above and execute it - you should now be looking at a list of the world's countries.
It's traditional to express a country's size in terms of how many times you could fit Wales into it - so let's do this! First create the following columns in a query:
|Column||What it should show|
|AreaLeftOver||The remainder when you divide a country's area by the area of Wales|
|WalesUnits||The number of exact times that the area of Wales divides a country's area, once you've subtracted the area left over as calculated above|
You'll need to know that Wales is 20,761 square kilometres in area!
Now extend your query to show a text description of how many times each country could accommodate Wales:
The first few countries in alphabetical order.
Finally, change your query's sort order so that it lists countries with the closest in size to Wales first:
El Salvador is closest in size to Wales, followed by Slovenia (the first is slightly larger, the second slightly smaller).
You may find the ABS function useful to show the absolute value of the difference in sizes for each country. If you're wondering why Wales isn't top of the list ... it's not a country in its own right!
Save this query as How many whales, then close it down.
KmSquared % 20761 AS AreaLeftOver,
(KmSquared - (KmSquared % 20761))/20761 AS WalesUnits,
CONCAT((KmSquared - (KmSquared % 20761))/20761, ' x Wales plus ', KmSquared % 20761, ' sq. km.') AS WalesComparison
ORDER BY ABS(20761 - KmSquared) ASC
In the SQL script used to design and fill the CountriesByArea table, there is no entry for Wales.
There doesn't need to be! You can assess how close in area a country is to Wales without including Wales in your list of countries.
, ROUND(KmSquared/20761, 0) as 'WalesUnits'
, (Kmsquared % 20761) as 'AreaLeftOver'
CAST(ROUND((KmSquared/20761), 0) as varchar(10)) < 1
'Smaller than Wales'
CAST(ROUND((KmSquared/20761), 0) as VARCHAR(10)) + ' x ' + ' Wales plus ' +
CAST( (KmSquared % 20761) as VARCHAR(10)) + ' sq. km.'
END as 'Wales Comparison'
Order By ABS(KmSquared - 20761)
if i have array of numbers
10, 9.8, 10.1, 9.5, 10.8, 9.7
I would like to arrange this array by nearest to 10.
To compare this array to 10. I am going to subtract array values from 10:
(10-10), (10 - 9.8), (10-10.1), (10-9.5), (10-10.8), (10-9.7)
0, 0.2, -0.1, 0.5, -0.8, 0.3
To compare numbers i have to consider both postives and negatives, so i am going to use absolute values
0, 0.2, 0.1, 0.5, 0.8, 0.3
Now let's arrange these numbers nearest to 10:
0, 0.1, 0.2, 0.3, 0.5, 0.8
Now write down with corresponding numbers:
10, 10.1, 9.8, 9.7, 9.5, 10.8
So to summarize, i arranged numbers by using ABS(MyNumbers - 10)
I managed to get until the last part but still when sorting the results as requested the are two countries misssing, any ideas on the tweak that needs to be done to the query to get these two counties listed?
,ABS(KmSquared/20761) AS WalesUnits
,ABS(KmSquared)-((KmSquared/20761)*20761) AS AreaLeftOver
WHEN KmSquared > 20761 THEN CAST(KmSquared/20761 AS VARCHAR(20))
+ ' x ' + 'Wales plus' + ' ' + CAST((KmSquared)-((KmSquared/20761)*20761
) AS VARCHAR(25)) + ' ' + 'sq. km.'
WHEN KmSquared <= 20761 THEN 'Smaller than Wales'
END AS WalesComparison
WHERE kmSquared <= ALL (SELECT KmSquared
WHERE ABS(20761 - KmSquared) < 500)
I could solve till the second last requirement. The final one seems tough .... can anyone help with the trick?
at the first look it seems though, but it is quite simple. You want to order by KmSquared ascending in the near of Wales (size=20761). So what if Wales itself would be in the list? It's KmSquared would be 20761. The difference WalesSize-20761=0 the next greater one could be (WalesSize+x)-20761=x ans so on...
But what about the smaler ones? Same thoughts. And here comes ABS function in play to get rid of the minus...Clear now? Or do u want the result?