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.

Software ==> SQL  (198 exercises)
Version ==> Any version of SQL Server
Topic ==> Aggregation and grouping  (8 exercises)
Level ==> Harder than average
Subject ==> SQL training
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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Create a query which shows two statistics for each category initial:

  1. The number of events for categories beginning with this letter; and
  2. 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:

Category initials

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.

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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24 Sep 21 at 15:52

           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)