WISE OWL EXERCISES
- Simple Queries (4)
- Setting criteria using WHERE (5)
- Calculations (7)
- Calculations using dates (4)
- Basic joins (8)
- More exotic joins (2)
- Aggregation and grouping (8)
- Views (5)
- Subqueries (5)
- Stored procedures (5)
- Variables (8)
- Parameters and return values (11)
- Testing conditions (1)
- Looping (3)
- Scalar functions (6)
- Transactions (5)
- Creating tables (5)
- Temporary tables and table variables (9)
- Table-valued functions (6)
- Derived tables and CTEs (13)
- Dynamic SQL (4)
- Pivots (2)
- Triggers (2)
- Archived (70)
SQL | Derived tables and CTEs exercise | Use a CTE to avoid including the same CASE statement twice
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 one of more of the courses 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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The aim of this exercise is to count the number of events by a column called Era which you'll calculate, without including this calculation twice:
Here's what NOT to do - we want to avoid repeating the same calculation twice.
To do this, you can do the calculation in two bites, using a CTE to hold the intermediate stage. First create a query to show the era for each event:
You could peek at the expression at the start of this exercise to get help on how to calculate the era!
Now store this as a CTE, and write a query using it which shows the number of events per era:
What the entire query should show when you run it.
Save this query as Epoch-making, and close it down.