Exercise: Use a variable to accumulate an episode's enemy names

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.

The answer to the exercise will be included and explained if you attend the Wise Owl course listed below!

Category ==> SQL  (115 exercises)
Topic ==> Variables  (8 exercises)
Level ==> Average difficulty
Course ==> Advanced SQL
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First (if you haven't already done so) run the script shown above to generate the Doctor Who training database.

The aim of this exercise is to show a list of all of the Doctor's enemies for a given episode:

List of companions

What you would see for episode 15.

To start this, create a variable in a new query to hold the episode number:

-- choose a specific episode

DECLARE @EpisodeId int = 15

Now create another variable to hold the accumulated list of episode names:

-- variable to hold the list of enemies

DECLARE @EnemyList varchar(100) = ''

Write a SELECT statement which accumulates the list of enemy names for the chosen episode in a variable.  The basis of this will be a statement starting like this:

SELECT

-- add in each enemy name

@EnemyList = @EnemyList + ...

When you've done this, complete your query to show your results:

-- show the results

SELECT

@EpisodeId as 'Episode id',

@EnemyList AS 'Enemies'

Optionally, save this query as Know your enemies.sql, then close it down.

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