You have two tables named Customers and Orders created in Microsoft Office Access 2010. In
Orders table, each order has a customer ID. You want to correspond it to a record in the Customers
table. Which of the following will you use to accomplish the task?
Each correct answer represents a complete solution. Choose all that apply.
A.
Entity integrity
B.
Domain integrity
C.
Primary key
D.
Foreign key
Explanation:
In order to accomplish the task, you should use the following:
Primary key: A table usually has a column or combination of columns whose values uniquely identify
each row in the table. This column (or columns) is called the primary key. Primary key ensures that
no duplicate or null values are entered in the column (or columns) defined as primary key columns.
This enforces integrity of the table. A primary key can be created by defining a primary key
constraint while creating or altering a table. A table can have only one primary key constraint. As
primary key constraints ensure uniqueness, they are often defined by using an identity column.
Foreign key: A foreign key is a column or combination of columns used to establish and enforce a
relationship between the data in two tables. This relationship is created by adding a column(s) in one
of the tables to refer to the other table’s column(s) protected by a PRIMARY KEY or UNIQUE
constraint. This column becomes a foreign key in the first table. A foreign key can be created by
defining a FOREIGN KEY constraint when creating or altering a table.
Answer A is incorrect. Entity integrity enforces the uniqueness of rows in a table. The uniqueness of
rows can be enforced by the identifier column(s) through indexes, UNIQUE constraints, PRIMARY
KEY constraints, or IDENTITY properties.
Answer B is incorrect. Domain integrity enforces data validity by restricting the data type, valid
values (using CHECK constraints and rules), and range of possible values (using FOREIGN KEY
constraints) for columns in a table.