Question

In order to include an attribute Name to the teaches relation which of the following command is used?

(a) Alter table teaches include Name;

(b) Alter table teaches add Name;

(c) Alter table teaches add Name varchar;

(d) Alter table teaches add Name varchar(20);

I had been asked this question in an international level competition.

The question is from Querying database part-1 DDL in section Database Systems Design and Implementation of Database Management

Answer 1

Right choice is (d) Alter table teaches add Name varchar(20);

Easy explanation - The form of the alter table command is

alter table r add AD;

where r is the name of an existing relation, A is the name of the attribute to be added, and D is the type of the added attribute.