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Software ==>	SQL (202 exercises)
Topic ==>	Subqueries (8 exercises)
Level ==>	Average difficulty
Subject ==>	SQL training

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

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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:	Bhavya59
When:	02 Aug 24 at 09:15

SELECT [CountryName]

FROM tblCountry c

WHERE (

SELECT COUNT(*) FROM tblEvent e

WHERE e.CountryID=c.CountryID

)>8

ORDER BY CountryName

From:	Orin
When:	03 Mar 24 at 12:03

Before looking at the solution, I did not figure out it was possible to link the countries from Country and Event inside the correlation.

So I did the trick with a Distinct :

USE WorldEvents

SELECT Distinct
c.CountryName
-- ,count(e.EventID)
FROM
tblEvent as e
INNER JOIN tblCountry as c
ON e.CountryID = c.CountryID
WHERE
(SELECT count(e2.EventID) FROM tblEvent as E2
WHERE e.CountryID = e2.CountryID) > 8
--GROUP BY
-- c.CountryName

From:	Devender
When:	20 Jan 24 at 07:56

use WorldEvents

--using group by

select c.countryname from tblCountry c

join tblEvent e

on c.CountryID=e.CountryID

group by CountryName

HAVING COUNT(e.EventID) > 8

-- using sub queri

select c.countryname

from tblCountry c

where (select COUNT(e.countryid)

from tblEvent e

where e.CountryID = c.CountryID

group by e.countryid) > 8

order by CountryName

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

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

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

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

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

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

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

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

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

Got it.
Tnx

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EXERCISE TOPIC

SQL EXERCISES

SQL EXERCISES

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

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