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Software ==>	SQL (129 exercises)
Topic ==>	Basic joins (9 exercises)
Level ==>	Average difficulty
Subject ==>	SQL training

Use inner joins to link four tables to show Dr Who enemies by author

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.

Write a query using inner joins to show all of the authors who have written episodes featuring the Daleks. You may find the following relationship diagram useful to refer to:

How to get from enemies to authors in 3 easy jumps.

You should find that there are 16 such episodes!

When you've finished, save this as Enough joins for now, 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:	sipi41
When:	15 May 22 at 20:32

Reply to sipi41

The exercise says: LIST AUTHORS

select a.AuthorId, a.AuthorName
from tblAuthor a
inner join tblEpisode e
   on a.AuthorId = e.AuthorId
inner join [tblEpisodeEnemy] EpEn
   on EpEn.EpisodeId = E.EpisodeId
inner join [tblEnemy] enemy
   on enemy.EnemyId = EpEn.EnemyId
WHERE enemy.EnemyName LIKE 'Daleks'
GROUP BY a.AuthorId, a.AuthorName

From:	Miller
When:	18 Dec 18 at 20:31

Reply to Miller

select [EpisodeEnemyId], e.[EnemyName],[EpisodeNumber],[AuthorName]
from [dbo].[tblEpisodeEnemy] as epe
inner join [dbo].[tblEnemy] as e
on epe.EnemyId= e.EnemyId
inner join [dbo].[tblEpisode] as e1
on epe.EpisodeId = e1.EpisodeId
inner join [dbo].[tblAuthor] as a
on e1.AuthorId= a.AuthorId
where EnemyName like '%Daleks%'

From:	LACubico
When:	25 Sep 18 at 15:35

Reply to LACubico

Use inner joins to link four tables to show Dr Who enemies by author.

USE DoctorWho
select a.AuthorId,a.AuthorName,
b.Title,b.episodetype,
c.EnemyId, d.EnemyName
from tblAuthor as a
inner join tblEpisode as b on
a.AuthorId = b.AuthorId
inner join tblEpisodeEnemy as c on
c.EpisodeId = b.EpisodeId
inner join tblEnemy as d on
d.EnemyId = c.EnemyId
where d.EnemyName = 'Daleks'

From:	grao
When:	05 Nov 17 at 18:42

Reply to grao

So is this the code?

use doctorwho

Select authorname

from tblauthor as a
inner join tblepisode as epi
on a.authorid = epi.authorid

inner join tblepisodeenemy as ene
on epi.episodeid = ene.episodeenemyid

inner join tblenemy as enemy
on enemy.enemyid = ene.episodeenemyid

where title like '%Daleks%'

From:	bhilarev
When:	25 Oct 17 at 07:14

Reply to bhilarev

I just get only four rows ,

Select
x.AuthorName,y.EpisodeNumber,y.Title,y.EpisodeDate
From Author As x
INNER JOIN Episode As y
ON x.AuthorId = y.AuthorId
Where Title Like '%Daleks%';

Is this query correct?

From:	linjom
When:	19 Apr 18 at 06:32

Reply to linjom

Should have been ..

enemyname like' %Dalek%'

From:	Andy B
When:	25 Oct 17 at 08:44

Reply to Andy B

You're showing all the episodes whose titles contain the word Dalek, rather than all episodes which feature the Daleks. So for example an episode entitled "Little tin men from space" might feature the Daleks, but wouldn't appear in your query.

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Use inner joins to link four tables to show Dr Who enemies by author

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