Exercise: Fn to count trainer ids

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.

The answer to the exercise will be included and explained if you attend the relevant Wise Owl course (sadly, only in the UK for now).

Category ==> SQL  (156 exercises)
Topic ==> Archived  (70 exercises)
Level ==> Average difficulty
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).

You need a minimum screen resolution of about 700 pixels width to see our exercises. This is because they contain diagrams and tables which would not be viewable easily on a mobile phone or small laptop. Please use a larger tablet, notebook or desktop computer, or change your screen resolution settings.

If you haven't already done so, run the stored procedure in the above folder to generate a database of training courses and delegates.

Each row in the tblSchedule table contains a column called TrainerIds, giving details of who is assigned to train on the course:

SQL exercise - Avoiding scalar functions (image 1)

Scheduled course 1, for example, has trainers number 21 and 93 assigned to it

We will create a function called fnCountIds to count how many trainers there are assigned to each course (note that exactly the same function could also count how many resources are assigned).  The following code excerpt contains an idea to help you do this:

SQL exercise - Avoiding scalar functions (image 2)

Count the number of trainers by seeing how long the string of ids is with and without its commas, and then taking the difference between these two numbers

Incorporate your function in a query to count the number of trainers assigned to a course:

SQL exercise - Avoiding scalar functions (image 3)

The first few rows of the final query, sorted by course start date

Optionally, save the code to generate your function as Count trainers.sql, then close it down.

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