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Practise SQL in your browser with SQL Fiddle
Part eight of a sixteen-part series of blogs

Some of our poor delegates don't have the luxury of a home computer to install SQL on (even worse some have made bad life choices and picked a Mac). The good news is that you can still practise your SQL skills in your web browser, using the impressive SQL Fiddle site. Have no fear, SQL Fiddle is here, a browser based sandbox to bring you cheer!

  1. Installing and configuring SQL Fiddle
  2. SQL Fiddle Exercise 1 - SELECT
  3. SQL Fiddle Exercise 2 - Order By
  4. SQL Fiddle Exercise 3 - Numeric Filters
  5. SQL Fiddle Exercise 4 - Date Filter
  6. SQL Fiddle Exercise 5 - Text Filters
  7. SQL Fiddle Exercise 6 - Cast or Convert Functions
  8. SQL Fiddle Exercise 7 - Conditional Function (this blog)
  9. SQL Fiddle Exercise 8 - Counting Words
  10. SQL Fiddle Exercise 9 - Formatted Dates
  11. SQL Fiddle Exercise 10 - Date Calculations
  12. SQL Fiddle Exercise 11 - Inner Join
  13. SQL Fiddle Exercise 12 - Outer Join
  14. SQL Fiddle Exercise 13 - Grouping Data
  15. SQL Fiddle Exercise 14 - Having
  16. SQL Fiddle Exercise 15 - All together now!

Posted by Sam Lowrie on 01 July 2021

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SQL Fiddle Exercise 7 - Conditional Function

There are two ways to test conditions in SQL: the IIF function or the CASE keyword.  Let's try both!  Start by using the IIF function to classify purchases (somewhat arbitrarily) by the quantity bought:

SQL Fiddle

Using IIF, classify each product under 6 as Poor and anything else as Good.  This query shows the first 3 of 80 rows.

This is fine, but I'd like to be more discerning with my categorisation. Depending on someone's performance they will receive a bonus.  Use the CASE WHEN keyword to determine this:

SQL Fiddle

Any purchase below 4 quantity will get 0% of the price as a bonus; between 4 and 8 they will get 10% of the price; anything else gets 15%.

Remember WHEN using a CASE and something is true, THEN something else should happen before the END.

Check out the answer here.

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