Question

Point out the wrong statement.

(a) Table constraints must be used when more than one column must be included in a constraint

(b) A column constraint is specified as part of a column definition and applies only to that column

(c) A table constraint is declared independently from a column definition and can apply to more than one column in a table

(d) Primary keys allow for NULL as one of the unique values

The question was asked in examination.

This is a very interesting question from Constraints topic in division Manipulating Data with Select of SQL Server

Answer 1

The correct option is (d) Primary keys allow for NULL as one of the unique values

To elaborate: Primary keys also enforce uniqueness, but primary keys do not allow for NULL as one of the unique values.