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SQL | Derived tables and CTEs exercise | Use a CTE to show events containing this and that
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 one of more of the courses 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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This exercise shows how you can use a CTE to make a complicated question simple, by dividing it into two or more parts.
First create a query to list out for each event id the positions (if any) of the words this and that:
The first few events in the list - the last two columns give the position (if any) at which the words this and that can be found.
As an example, CHARINDEX('too','This too shall pass',1) would return 6, since the word too starts at the 6th letter of the given text (if you begin counting at the 1st character).
Now using this as a CTE, show the two events which contain both words in the right order (ie this followed by that). You'll need to join your CTE to the events table, so that you can pick up on the event name and event date, and display them.
The EventDetails column for these two events contains the words this and that, in this order.
Here's the sort of thing you'd have had to write without a CTE (showing how useful CTEs are!):
CHARINDEX('this',e.EventDetails,1) AS ThisPosition,
CHARINDEX('that',e.EventDetails,1) AS ThatPosition
FROM tblEvent AS e
-- must contain both strings ...
CHARINDEX('this',e.EventDetails,1) > 0 and
CHARINDEX('that',e.EventDetails,1) > 0 and
-- ... in the right order
Save your query as This and that revisited, and close it down.