SQL | Parameters and return values exercise | Using Output parameters

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Software ==> SQL  (198 exercises)
Version ==> Any version of SQL Server
Topic ==> Parameters and return values  (11 exercises)
Level ==> Harder than average
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.

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First write a stored procedure to show which country has the most events:

Output parameters Countries Events

Your query should show these results - we now want to capture these two bits of information, and return them to the calling query.

Add two output parameters to your procedure:

Parameter What it should take
@TopCountry The country name
@EventCount The number of events for it

The parameters must have a default value, and must include the word OUTPUT.

Amend your procedure to capture the country name and number of events in these variables, within your SELECT clause:

SELECT TOP 1

--Values go into parameters just like variables

@TopCountry = CountryName

,@EventCount= COUNT(E.CountryID)

FROM ...

Open a new window to execute the procedure. Create two variables to store the values held in the output parameters.

Using output parameters will give you headaches.

The tricky part is setting the parameters equal to the variables: remember to specify OUTPUT!

Select the two variables to check the information has been successfully output.

 Optionally save this as Most Eventful Country.sql, then close it down.

You can unzip this file to see the answers to this exercise, although please remember this is for your personal use only.
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