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

Use grouping to show how many episodes each Doctor Who author wrote

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 following diagram shows how the authors and episodes tables are related:

You're probably familiar with this by now!

Use this to show for each author:

the number of episodes they wrote;
their earliest episode date; and
their latest episode date.

If you sort these so that the most prolific authors come first, here are the first few of the 25 rows you should see:

Those who know their Doctor Who won't be surprised at the two leaders.

Save this query as Blink was the best, 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:	Shalu
When:	15 Jan 22 at 17:43

Reply to Shalu

select ta.AuthorName,count(te.EpisodeID) countE,min(EpisodeDate) EarliestDate,MAX(EpisodeDate) LatestDate
from tblAuthor ta inner join tblEpisode te
on ta.AuthorId=te.AuthorId
group by ta.AuthorName
order by countE desc

From:	Wise Owl 2
When:	08 Nov 21 at 13:23

Reply to Wise Owl 2

with aut as (
select count(title) as [Number of episodes wrote],AuthorId from tblEpisode
group by AuthorId
)
select a.Authorname,b.[Number of episodes wrote],max(c.episodeDate) as [Latest Episode Date],min(c.episodedate) as [Earliest Episode Date] from tblAuthor a
inner join aut b on a.AuthorId=b.authorId
inner join tblEpisode c on a.AuthorId=c.AuthorId
group by AuthorName,[Number of episodes wrote]
order by [Number of episodes wrote] desc

From:	walteragwe
When:	21 Jan 21 at 02:47

Reply to walteragwe

SELECT [AuthorName], COUNT([EpisodeId]) AS [# OF EPISODES],
   MIN([EpisodeDate]) AS [Earliest epi Date],
   max([EpisodeDate]) as [latest epi Date]
FROM [dbo].[tblAuthor] AS A INNER JOIN [dbo].[tblEpisode] AS E
   ON A.AuthorId = E.AuthorId
GROUP BY [AuthorName]
order by [# OF EPISODES] desc;
GO

From:	shahnawaz
When:	20 Jul 20 at 12:22

Reply to shahnawaz

select AuthorName, count(EpisodeNumber), EpisodeDate as [Earliest date], EpisodeDate as [Latest date] from
                               tblAuthor INNER JOIN tblEpisode ON tblAuthor.AuthorId=tblEpisode.AuthorId
                               group by AuthorName, EpisodeDate
                               order by [Earliest date] asc, [Latest date] desc

What is the problem with my code?

From:	Dintakurthi
When:	19 Nov 20 at 07:27

Reply to Dintakurthi

SELECT a.AuthorName,COUNT(a.AuthorId) AS Episodes,MIN(B.EpisodeDate) AS EarlistDate,MAX(B.EpisodeDate) AS LatestDate from tblAuthor a
INNER JOIN tblEpisode b on b.AuthorId=a.AuthorId
GROUP BY a.AuthorName,a.AuthorId
ORDER BY a.AuthorName ASC

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SQL EXERCISES

Use grouping to show how many episodes each Doctor Who author wrote

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