ch8

Question 1

database

Answer 1

a structure collection of items of data that can be accessed by application programs

Question 2

relational database

Answer 2

database where the data are linked together by an internal pointer

Question 3

table

Answer 3

a group of similar data in a database with rows for each instance of an entity and columns for each attribute

Question 4

candidate key

Answer 4

set of attribute where no tulip has the same value

Question 5

primary key

Answer 5

a unique identifier for a table and its a special case of candidate key

Question 6

secondary key

Answer 6

a set of attributes that is alternative to a primary key

Question 7

foreign key

Answer 7

a key in one table that refers to the primary key of another table

Question 8

referential integrity

Answer 8

a property of a database that does not contain any values of a foreign key that does not correspond to its matched primary key// data quality concept that ensures that when you make changes to data in one place, those changes are reflected in other related records

Question 9

index

Answer 9

a data structure built from one or more columns in a database table to speed up searching for data

Question 10

normalisation

Answer 10

process of organizing data in database into two or more tables and the relationship between them to minimise redundancy

Question 11

1NF

Answer 11

the status in of a relational database where entities do not contain repeated groups of attribute

Question 12

2NF

Answer 12

the status of a relational database in which entities are in 1NF and any non key attributes depend on the primary key

Question 13

3NF

Answer 13

the status of a relational database in which entities are in 2NF and all non-key attributes are independent

Question 14

composite key

Answer 14

a set of attributes that form a primary key to provide a unique identifier for a table

Question 15

Database management system

Answer 15

systems software for the definition, creation and and manipulation of database

Question 16

data dictionary

Answer 16

a set of data that contains metadata for a database

Question 17

data modelling

Answer 17

the analysis and definition of the data structures required in a database and to produce a data model

Question 18

logical schema

Answer 18

a model of a database that is not specific to one DBMS

Question 19

developer interface

Answer 19

a software tool that allows the user to create items such as tables, forms and reports

Question 20

query processor

Answer 20

software that allows user to enter a criteria then find and return the appropriate result

Question 21

data definition language

Answer 21

to create, modify, and remove data structure that makes a relational database

Question 22

data manipulation language

Answer 22

to add, modify and delete data stored in relational database

Question 23

characteristic s of database in 3NF

Answer 23

no repeating groups of attributes
no partial dependencies
no non-key dependencies

Question 24

how access rights can be used to protect

Answer 24

1- access rights gives manager access to different elements by having different accounts
2- specific views can be assigned to managers

Question 25

why relational database is better than file based approach

Answer 25

1- reduces data redundancy: . because linked tables mean that each data item is stored only once
2- reduces data dependency: because the data is separate from the software so changes to the data do not require programs to be re-written
3- reduces data inconsistency: changes in one table will automatically update in another
4- Complex queries are easier to run: can provide different views, so user can only see specific aspect of the database