IBM DB2 11.1 Advanced DBA for Linux, UNIX, and Windows — Question 39

Which constraint can be used to ensure that identical values are never stored in a set of columns in a table?

Answer options

• A. NOT NULL
• B. Foreign key
• C. Primary key
• D. Informational constraint

Correct answer: C

Explanation

The correct answer is C, Primary key, as it enforces uniqueness for the specified columns, preventing duplicate entries. NOT NULL only ensures that a column cannot have null values, a Foreign key establishes a relationship between tables but does not enforce uniqueness, and an Informational constraint is not a standard type of constraint for managing uniqueness.