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- Aggregation and grouping (8)
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SQL | Aggregation and grouping exercise | Show the number / average length of events by category initial
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.
- 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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Create a query which shows two statistics for each category initial:
- The number of events for categories beginning with this letter; and
- The average length in characters of the event name for categories beginning with this letter.
Here are the first few rows you should get when you run your ever-so-slightly contrived query:
It looks like most events begin with categories beginning with an E (there are 5 such categories, which helps), but that Ns have it for the longest average event name length.
You'll need to use the following functions at some point: CAST or CONVERT, AVG, COUNT, LEN, UPPER and LEFT!
Save this query as P please bob, then close it down.
left (c.CategoryName ,1) as Category_Initial
, count (e.EventName) as Number_of_Events
, sum(len (e.EventName)) as Total_Length
, cast(avg( cast( len (e.EventName) as float ) ) as decimal(6,2) ) as AVG_Event_Name_Length
from [dbo].[tblEvent] e
left join [dbo].[tblCategory] c
on e.CategoryID = c.CategoryID
group by left (c.CategoryName ,1)