Exercise: Join events to categories, and then show empty categories

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

Category ==> SQL  (156 exercises)
Topic ==> Basic joins  (8 exercises)
Level ==> Average difficulty
Course ==> Introduction to SQL
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  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.

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Create a query which uses an inner join to link the categories table to the events table (they share a column/field called CategoryId):

Events and categories

The first few of the 459 events in reverse date order. We weren't sure of the correct category for the first one.

Change the inner join to an outer join, so that you show for each category its events - even when there aren't any:

Empty categories

If you scroll down to the bottom of your query, you'll see you now have a couple of extra rows, making 461 in total.

Add a WHERE clause to show only those categories which don't have any corresponding events:

The two empty categories

It seems unlikely they'll be any events for the first category, but you never know ...

 

Save this query as Empty categories, then close it down. 

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