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Software ==>	SQL (129 exercises)
Topic ==>	Subqueries (5 exercises)
Level ==>	Average difficulty
Subject ==>	SQL training

Create a correlated subquery to list out all countries having more than 8 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.

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).

Write a query which lists out countries which have more than 8 events, using a correlated subquery rather than HAVING.

That is: list the names of countries from the countries table where for each country the number of events matching the country's id is more than 8.

If you list the countries in alphabetical order, you should get:

Although your query should be easy to read, one disadvantage is that you can't see how many events there were for each country.

Save this query as Eventful countries, 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:

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From:	YUVA
When:	31 Jul 23 at 18:49

Reply to YUVA

Select
c.CountryName
from tblCountry c
where (select count(*) from tblEvent e where e.CountryID=c.CountryID )>8
order by c.CountryName

From:	Aravindh_sql
When:	29 May 22 at 16:32

Reply to Aravindh_sql

SELECT CountryName
FROM tblCountry INNER JOIN tblEvent
ON tblCountry.CountryID = tblEvent.CountryID
GROUP BY CountryName
HAVING COUNT(tblEvent.EventID) > 8

This Query Works fine.
Need not to write Sub-Query

From:	imti
When:	12 Feb 21 at 21:14

Reply to imti

with cte1 as
(
select c.countryname,(select COUNT(e.countryid)
       from tblEvent e
       where e.CountryID = c.CountryID
       group by e.countryid) as noocc
from tblcountry c)
select CountryName from cte1 where noocc>8

From:	Dintakurthi
When:	20 Nov 20 at 06:23

Reply to Dintakurthi

This is also a perfect output:

SELECT A.CountryName
FROM TblCountry A
INNER JOIN
(
SELECT TE.CountryID, COUNT(TE.EventID) XYX
FROM tblEvent TE
GROUP BY TE.CountryID HAVING COUNT(TE.EventID) > 8) B ON A.CountryID = B.CountryID
)

From:	Anita
When:	27 Jun 20 at 17:55

Reply to Anita

We can get the country name and no of event occured without even using a subquery:

select distinct count([EventName]) as No_of_event,[CountryName] from [tblEvent] e
inner join [dbo].[tblCountry] c on e.CountryID = c.CountryID
group by [CountryName]
having count([EventName]) >8

From:	mgroesink
When:	11 Jun 20 at 15:56

Reply to mgroesink

Not a big deal to show also the numbers of events per country:

select c.CountryName , (select count(*) from tblEvent where CountryID = C.CountryID) [Number of events]
from tblCountry c

From:	ShukiMolk
When:	12 Apr 20 at 23:38

Reply to ShukiMolk

Couldn't do it without using HAVING in the subquery :-(
Anyone has any ideas?

DISTINCT cntr.CountryName
FROM
   tblEvent evnt
   INNER JOIN tblCountry cntr
   ON evnt.CountryID = cntr.CountryID
WHERE evnt.CountryID IN
--countryID for countries that has more than 8 events
       (
       SELECT
       evnt.CountryID
       --,count(evnt.EventID) AS [Number of events]
       FROM
           tblEvent evnt
           INNER JOIN tblCountry cntr
           ON evnt.CountryID = cntr.CountryID
       GROUP BY
       evnt.CountryID,
       cntr.CountryName
       Having
       count(evnt.EventID) > 8
       )

From:	Thomas
When:	16 Apr 20 at 18:01

Reply to Thomas

Hi,

Looks like this is working:

SELECT
   c.CountryName
FROM
   tblCountry c
WHERE
   8 < (
       SELECT
           COUNT(e.EventID)
       FROM
           tblEvent e
       WHERE
           e.CountryID = c.CountryID
   )
Order By
   c.CountryName;

From:	ShukiMolk
When:	21 Apr 20 at 16:44

Reply to ShukiMolk

Got it.
Tnx

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SQL EXERCISES

Create a correlated subquery to list out all countries having more than 8 events

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