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Introduction
The ISNULL() function
The COALESCE() function
The NULLIF() function
Summary
16. Summary

## Instruction

Nicely done! Now it's time to review what we've learned:

• the IS NULL operator checks if the column is NULL,
• the IS NOT NULL operator checks if the column is not NULL,
• the ISNULL() function finds NULLs and replaces them with the value given in the second argument,
• the NULLIF(x, y) function returns NULL if x = y and x otherwise,
• COALESCE(x, y, ...) returns the first non-NULL argument or replaces a NULL with the value given in the second argument.

Are you ready for a short quiz?

## Exercise

Click to continue.