Multiple choice technology databases

Which is not a type of constraint

  1. primary key

  2. unique

  3. null

  4. check
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

Database constraint types include PRIMARY KEY, UNIQUE, NOT NULL, CHECK, FOREIGN KEY, and others. 'null' by itself is not a constraint - it describes the absence of a value. 'NOT NULL' would be a valid constraint type, but the option simply says 'null'.

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