SQL | Calculations exercise | Show how big countries are in relation to Wales

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Software ==> SQL  (198 exercises)
Version ==> Any version of SQL Server
Topic ==> Calculations  (7 exercises)
Level ==> Harder than average
Course ==> Introduction to SQL
Before you can do this exercise, you'll need to download and unzip this file (if you have any problems doing this, click here for help). Once you've done this:
  1. Go into SQL Server Management Studio;
  2. Open the SQL file you've just unzipped (you can press CTRL + O to do this); then
  3. Execute this script.

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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:

Wales list

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:

Closeness to Wales

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. 

This page has 5 threads Add post
hjay629   Reply to hjay629Reply
18 Feb 19 at 23:28

--SPOILER--

ANSWER:

SELECT
Country
, KmSquared
, ROUND(KmSquared/20761, 0) as 'WalesUnits'
, (Kmsquared % 20761) as 'AreaLeftOver'
, CASE 
            WHEN 
                      CAST(ROUND((KmSquared/20761), 0) as varchar(10)) < 1 
            THEN 
                      'Smaller than Wales'
            ELSE 
                      CAST(ROUND((KmSquared/20761), 0) as VARCHAR(10)) +  ' x '  +  ' Wales plus ' + 
                      CAST( (KmSquared % 20761) as VARCHAR(10)) + ' sq. km.' 
             END as 'Wales Comparison'
FROM
CountriesByArea
Order By ABS(KmSquared - 20761)

chaluvadi   Reply to chaluvadiReply
07 Sep 18 at 17:05

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)

gemini132   Reply to gemini132Reply
13 Aug 18 at 13:12

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?

SELECT Country
,KmSquared
,ABS(KmSquared/20761) AS WalesUnits
,ABS(KmSquared)-((KmSquared/20761)*20761) AS AreaLeftOver
,CASE
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
FROM CountriesByArea
WHERE kmSquared <= ALL (SELECT KmSquared 
FROM CountriesByArea
WHERE ABS(20761 - KmSquared) < 500)

DataDriven   Reply to DataDrivenReply
18 Jun 18 at 23:43

Can anyone help me with the query for text description of how many times each country could accommodate Wales?

linjom   Reply to linjomReply
17 Apr 18 at 13:17

I could solve till the second last requirement. The final one seems tough .... can anyone help with the trick?

morguel   Reply to morguelReply
22 Apr 18 at 08:49

Hi,

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?

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