Databases Reference
In-Depth Information
APPENDIX
D
REVIEW QUESTIONS
MANAGEMENT
1. Redundancy is the duplication of data or the storing of the same data in more than one place. Redun-
dancy wastes space, makes the updating of data more cumbersome and time-consuming, and can
lead to inconsistencies.
3. An entity is a person, place, object, event, or idea for which you want to store and process data.
An attribute, which is also called a field or column in many database systems, is a characteristic
or property of an entity.
5. A database is a structure that can store information about multiple types of entities, the attributes
of those entities, and the relationships among the entities.
7. An E-R diagram represents a database in a visual way by using a rectangle for each entity, using a
line to connect two entities that have a relationship, and placing a dot at the end of a line to indi-
cate the “many” part of a one-to-many relationship.
9. Database design is the process of determining the table structure of the desired database.
11. It is possible to get more information from the same amount of data by using a database approach
as opposed to a nondatabase approach because all data is stored in a single database, instead of being
stored in dozens of separate files, making the process of obtaining information quicker, easier, and
even possible in certain situations.
13. The DBA (database administrator or database administration) is the central person or group in an
organization in charge of the database and the DBMS that runs the database. The DBA attempts
to balance the needs of individuals and the overall needs of the organization.
15. An integrity constraint is a rule that the data in a database must follow. A database has integrity
when the data in it satisfies all established integrity constraints. A good DBMS should provide an
opportunity for users to incorporate these integrity constraints when they design the database. The
DBMS then should ensure that these constraints are not violated.
17. Data independence is the property that lets you change the structure of a database without requir-
ing you to change the programs that access the database. With data independence, you easily can
change the structure of the database when the need arises.
19. The more complex a product is in general (and a DBMS, in particular, is complex), the more diffi-
cult it is to understand and correctly apply its features. As a result of this complexity, serious prob-
lems may result from mistakes made by users and designers of the DBMS.
21. The great complexity of a database structure makes recovery more difficult. In addition, many users
update the data at the same time, which means that recovering the database involves not only
restoring it to the last state in which it was known to be correct, but also performing the complex
task of redoing all the updates made since that time.
CHAPTER 2—THE RELATIONAL MODEL 1:
1. A relation is a two-dimensional table in which (1) the entries in the table are single-valued; (2) each
column has a distinct name; (3) all of the values in a column are values of the same attribute; (4)
the order of the columns is immaterial; (5) each row is distinct; and (6) the order of the rows is
immaterial.
