Question

______ constraint ensures that no two 'rows' have same value in specified column / columns
1. All option are wrong
2. Check
3. Unique
4. Default

Answer 1

Correct Answer - Option 3 : Unique

Concept 

CHECK

The CHECK constraint is used to limit the value range that can be placed in a column.

UNIQUE

The UNIQUE constraint ensures that no two 'rows' have the same value in specified column/columns.

DEFAULT

The DEFAULT constraint is used to provide a default value for a column.

Therefore correct answer Option 2