Databases · Junior · Question 5 of 75

What does the `NOT NULL` constraint do?

✓Correct answer: Forbids storing NULL in the column
2Forbids duplicate values in the column
3Sets the default value to 0

Explanation

Use UNIQUE to forbid duplicates and DEFAULT to set a default value. Marking required columns NOT NULL catches bugs early.

Further reading

PostgreSQL: Constraints ↗

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