SQL | Table-valued functions exercise | Create a function to list episodes for a given series and author

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Software ==> SQL  (198 exercises)
Version ==> Any version of SQL Server
Topic ==> Table-valued functions  (6 exercises)
Level ==> Average difficulty
Subject ==> SQL training
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First (if you haven't already done so) run the script shown above to generate the Doctor Who training database.

Create a function to list out the episodes for any given series number and part of an author name.  This could begin: 

CREATE FUNCTION fnChosenEpisodes(

@SeriesNumber int,

@AuthorName varchar(100)

)

RETURNS TABLE

AS

For example, you could run this SQL query:

SELECT * FROM dbo.fnChosenEpisodes(1,'russell')

This would show the 9 series one episodes written by Russell T. Davies:

List of episodes

The first 2 or 3 of the 9 episodes in series 1 written by Russell T. Davies

Functions can't have optional parameters, but you can pass dummy values and detect them.  Amend your function so that it shows:

  • Episodes for any series if you pass the first argument as Null;
  • Episodes for any author if you pass the second argument as Null.

To help you know whether you've succeeded, here's what 4 possible combinations should show:

-- there is 1 episode written by Steven Moffat for series 2

SELECT COUNT(*) FROM dbo.fnChosenEpisodes(2,'moffat')

-- -- there are 14 episodes in series 2 (for any author)

SELECT COUNT(*) FROM dbo.fnChosenEpisodes(2,null)

-- there are 32 episodes written by Steven Moffat (for any series)

SELECT COUNT(*) FROM dbo.fnChosenEpisodes(null,'moffat')

-- there are 117 episodes (any series, any author)

SELECT COUNT(*) FROM dbo.fnChosenEpisodes(null,null)

Optionally, save your query as Series and author.sql, 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.
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