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Software ==>	SQL (129 exercises)
Topic ==>	Aggregation and grouping (8 exercises)
Level ==>	Average difficulty
Subject ==>	SQL training

Group by 2 fields and use HAVING clause to show popular combinations

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.

If you haven't already done so, run the script in the above folder to generate the Doctor Who database.

The tables you'll need for this exercise are as follows:

You'll need to link each episode to its author and its doctor.

Write a query to list out for each author and doctor the number of episodes made, but restrict your output to show only the author/doctor combinations for which more than 5 episodes have been written. Here's what you should see:

Here we've sorted the rows so the most common combination appears first.

You'll need to use the HAVING clause. Remember that sweaty feet will give horrible odours!

Save this as Favourite combos, 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:	Rupchand7
When:	14 Nov 23 at 05:59

Reply to Rupchand7

select AuthorName, DoctorName, count(episodeid) as Episodes from tblauthor join tblepisode
on tblauthor.authorid = tblepisode.authorid join tbldoctor on tblepisode.doctorid = tbldoctor.doctorid
group by authorname, doctorname having count(episodeid) >5 order by Episodes desc

From:	sardor4ik
When:	01 Sep 22 at 09:22

Reply to sardor4ik

select AuthorName, doctorname,count(EpisodeId)as episodes from tblAuthor a
join tblEpisode e on a.AuthorId=e.AuthorId
join tblDoctor d on d.DoctorId=e.DoctorId
group by AuthorName, doctorname having count(EpisodeId)>5
order by 3 desc

From:	walteragwe
When:	21 Jan 21 at 03:09

Reply to walteragwe

SELECT [AuthorName],[DoctorName],COUNT([EpisodeId]) AS [No of episodes]
FROM [dbo].[tblAuthor] A INNER JOIN [dbo].[tblEpisode] E
ON A.AuthorId = E.AuthorId INNER JOIN [dbo].[tblDoctor] D
ON E.DoctorId = D.DoctorId
GROUP BY [AuthorName],[DoctorName]
HAVING COUNT([EpisodeId]) > 5
ORDER BY [No of episodes] DESC;
GO

From:	smyndlo
When:	24 Nov 19 at 13:54

Reply to smyndlo

SELECT
       au.AuthorName Writer, --1st Table
       Doc.DoctorName Doctor, --2nd Table
       COUNT(Ep.EpisodeId) 'Num Of Episodes' --3rd Table
FROM tblAuthor AS Au
   INNER JOIN tblEpisode AS Ep
   ON Au.AuthorId = Ep.AuthorId
   INNER JOIN tblDoctor Doc
   ON Doc.DoctorId = Ep.DoctorId
GROUP BY Au.AuthorName, Doc.DoctorName
HAVING COUNT(Ep.EpisodeId) > 5
ORDER BY [Num Of Episodes] Desc

From:	Andy B
When:	25 Nov 19 at 09:33

Reply to Andy B

We don't normally post answers to exercises, as it removes the incentive for people to try them, but I've made an exception for this because the query is so well-written and presented!

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SQL EXERCISES

SQL EXERCISES

Group by 2 fields and use HAVING clause to show popular combinations

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