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Introduction
Simple CASE WHEN
6. Simple CASE WHEN with NULLs
Searched CASE WHEN
CASE WHEN with aggregates
CASE WHEN with GROUP BY
Summary

Instruction

That's correct! Having gone through Part 5 about NULLs, you might want to ask: okay, but how do NULLs behave in CASE WHEN?

The answer is pretty straightforward: NULL will always go to the ELSE part if you include it. Let's check this out in an exercise.

Exercise

For table candidate, show each candidate's id, preferred_contact and the third column which will print:

  • 'traditional' if the preferred_contact is 'mail',
  • 'modern' if it's 'mobile' or 'e-mail',
  • or 'other' otherwise.

Look what is shown for NULL values.