Databases 1

Question 1

what is a database?

Answer 1

its a collection of data items structured so that data can be searched and retrieved when necessary

Question 2

what is a flat file?

Answer 2

the entire base is stored in a single file and there is one row for each record and one column for each field

Question 3

what is data duplication?

Answer 3

this is the duplication of data

Question 4

what is data inconsistency?

Answer 4

the more often data has to be keyed the more chance there is for errors in data entry

Question 5

what is poor data integrity?

Answer 5

data that is erroneous or inconsistent is not reliable

Question 6

why is relationship databases more powerful?

Answer 6

its a more powerful way of storing data as the relationships allow data to be retrieved from a number of tables using a single query and there is less data redundancy

Question 7

what is a primary key?

Answer 7

consists of more than one attribute that identifies one record from any other

Question 8

what is a foreign key?

Answer 8

its a primary key in one entity which is included in another entity to link the two tables

Question 9

how are relationships formed?

Answer 9

foreign keys that link tables together

Question 10

constraint’s help control data integrity and fix problems such as:

Answer 10

entering project name in a field where a project name is expected

having two projects with the same project ID

maintaining data integrity

Question 11

what does the features of constraints provide?

Answer 11

allows us to set field properties, link tables and set constraints help to increase the reliability of the data

Question 12

what are some of the operations that can be allowed or disallowed to a user?

Answer 12

SELECT

INSERT

DELETE

ALTER

CREATE

Question 13

what can SQL allow you to do?

Answer 13

allows most users to query and manipulate data, as well as protect it from unwanted updates, deletions or other errors

Question 14

what is the relational models portability?

Answer 14

its standard

by adhering to the rules of the relational model you ensure that your data can be transferred between relational database systems relatively easily

Question 15

what is an attribute?

Answer 15

an individual data item within an entity.

Question 16

what in entity?

Answer 16

identifies an object about which data will be stored within the system

Question 17

what is composite key?

Answer 17

consists of more than one attribute to uniquely identify an entity occurrence or record

Question 18

what is a relationship?

Answer 18

its an established by a foreign key in one entity linking to the primary key in another

Question 19

what is referential integrity?

Answer 19

it ensures that data in one table does not contradict the data in another table

Question 20

what is data design?

Answer 20

identifying the relationship between data and creating a logical design which is best suited to the data required for a system

Question 21

what are the steps in designing a database?

Answer 21

first is to identify and state what data needs to be stored

from the statement of data requirements a conceptual data model is produced

Question 22

what is a logical data model?

Answer 22

when creating a logical data model entities and their relationships are identified with the keys. the attributes of each entity are also identified

a logical data model does not describe the physical structure of the real database

Question 23

what is a physical data model?

Answer 23

its derived from the logical data model and includes the specification of all tables and the columns inside them.

the physical data model contains the primary keys of each table and it specifies the relationship between the tables using foreign keys