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Revision
Comparisons with NULL
Functions with NULL
COALESCE to the rescue
15. Data types in COALESCE
NULLIF
Revision and practice

## Instruction

Excellent. Keep in mind, though, that both of the values in the function COALESCE must be of the same type. For instance, you can't write the following:

COALESCE(price,'--')

because price is a number and '–' is a text field. Such a query will return an error.

## Exercise

Check it out for yourself. Try to use COALESCE to show the product name and the launch_date or 'no date' when there is no launch_date.

Then press to go to the next exercise.