Exercise: Create a trigger to capture any changes made to countries

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

Category ==> SQL  (192 exercises)
Topic ==> Triggers  (2 exercises)
Level ==> Average difficulty
Course ==> Advanced SQL
Before you can do this exercise, you'll need to download and unzip this file (if you have any problems doing this, click here for help). Once you've done this:
  1. Go into SQL Server Management Studio;
  2. Open the SQL file you've just unzipped (you can press CTRL + O to do this); then
  3. 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 aim of this exercise is to use a trigger to write any country changes made into a separate table. Here is what the table should show if you rename Vietnam to Viet Nam and then insert and delete the (to date) fictitious country OwlLand:

Log of country changes

What the log table should show after these changes.

 

To start the ball rolling, create the table shown above with two columns:

Column What it should contain
CountryName The name of the country just inserted, edited or deleted
Change Whether this was inserted, deleted or changed

Now create a trigger to run after anyone changes a country.  This should capture two rows:

Row Notes
The old country name Take the deleted table's country name
The new country name Take the inserted table's country name

Note that when you update a table, you populate both the deleted and inserted tables.

Now create two more triggers:

Trigger What it should do
After insert Add a row to the changes table containing the new country's name
After delete Add a row to the changes table containing the name just deleted

When you're happy everything's working OK, optionally save your query as Catalonia perhaps.sql, then close it down. 

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