WISE OWL EXERCISES
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SQL | Calculations exercise | Show substitute values for nulls in one of 3 different ways
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.
You can learn how to do this exercise if you attend the course listed below!
- Go into SQL Server Management Studio;
- Open the SQL file you've just unzipped (you can press CTRL + O to do this); then
- Execute this script.
This will generate the database that you'll need to use in order to do this exercise (note that the database and script are only to be used for exercises published on this website, and may not be reused or distributed in any form without the prior written permission of Wise Owl).
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The tblContinent table lists out the world's continents, but there are gaps:
You need to fill in the gaps! Read on ...
Add up to 3 columns to show a message where a summary is missing:
This is what your query should show - see notes below.
Here's what your 3 columns should use:
|Column||How to get it|
|Using ISNULL||Use the IsNull function to substitute the words No summary for rows where the Summary column is null.|
|Using COALESCE||Do the same thing, but using the COALESCE function instead.|
|Using CASE||Use a CASE WHEN statement to show different things according to whether the Summary column is null or not.|
Take a moment to think which method you liked best, then save your query as Missing summaries and close it down.
The WorldEvents database table dbo.tblContinent that I downloaded doesn't have a third column. Is that the case for others?