WISE OWL EXERCISES
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SQL | Variables exercise | Create a comma-delimited list of events for a year
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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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Write a SQL statement which brings back the top 3 events in your year of birth, in event name order. You will need to use the YEAR function in the WHERE clause to do this, together with SELECT TOP 3 and an ORDER BY clause:
The events that you should return if you are ridiculously young enough to be born in 1992.
Running the SELECT statement will generate a number of rows, but variables can only hold one. What we'd really like to do is to join the events into a single string variable:
Much more compressed!
To do this, first create a VARCHAR variable (called @EventsInYear, say) to hold the event names.
Now amend your SQL statement so that it sets this variable to hold the concatenated event names. The syntax for getting this list to build can be tricky. Instead of simply putting variable = value, you need to set the variable equal to itself plus the value:
@Variable = @Variable + Column + ', '
This stops each new row from replacing the previous variable value, and instead adds text on to the last value (hence accumulating a list).
If the value of @Variable reads NULL when you show it at the end, try setting its initial value to a blank string.
Optionally save this query as Eventful Year.sql, then close it down.