The Relational Model and Normalization - Technical MCQs

Q1:

A key:

A must always be composed of two or more columns.

B can only be one column.

C identifies a row.

D identifies a column.

ANS:C - identifies a row.

A DBMS key is an attribute or set of an attribute which helps you to identify a row (tuple) in a relation(table). They allow you to find the relation between two tables. Keys help you uniquely identify a row in a table by a combination of one or more columns in that table.