Brainscape's Knowledge GenomeTM

Browse over 1 million classes created by top students, professors, publishers, and experts.


See full index

DATABASE SYSTEMS > Week 1 > Flashcards

Week 1 Flashcards

1
Q

what does DBMS mean

A

the software used to create and maintain data base systems

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

Are data and programs external to the DBMS

A

Yes they are external to the DBMS software as the DMS doesnt relate to the specific application

essentially all the relevant data isnt part of DBMS

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

what does meta data mean

A

The description of the data

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

What is a data model

A

concepts to describe the:
- structure of data
- the operations to manipulate these structures
- constraints

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

what is the database system

A

Both the DBMS software and the data itself

applications can also be included

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

Purpose of DBMS ( 4 things)

A

. defines a particular database in terms of its data types, structures and constraints

. create or load initial database onto a secondary storage medium

.Manipulating data:
- updating / removing data from a
database
- ACCESSING DATA THROUGH WEB APPS
- QUERYING , GENERATING REPORTS

. processing and sharing by multiple users and applicating programs WHILE ensuring all data is still valid and consistent

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

why is it important to define data types

A

To ensure only valid data types are in required fields keeping data consistent

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

advantages of DBMS

A

ADVANTAGES:
Controlling redundancy in data storage and in development and maintenance efforts.
* Providing multiple interfaces to different classes of users, facilitate sharing data across users.
* Restricting unauthorised access to data.
* Providing Storage Structures (e.g. indexes) for efficient
query processing (buffering/caching).
* Providing backup and recovery services.
* Representing complex relationships among data.
* Enforcing integrity constraints on the database.
* Drawing inferences and actions from the stored data using deductive and active rules

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

disadvantage of DBMS

A

Main inhibitors (costs) of using a DBMS:
o High initial investment and possible need for additional hardware.
o Overhead for providing generality, security, concurrency control,
recovery, and integrity functions.
* When a DBMS may be unnecessary:
o If the database and applications are simple, well defined, and not
expected to change.
o If there are stringent real-time requirements that may not be met
because of DBMS overhead.
o If access to data by multiple users is not required

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

what is a mini world

A

The real world domain that the database is designed for

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

What is an advantage of program data independence

A

.Caters for variety of (levels of) users
- user does not need to now specifics of the data to operate

. adapt to many different applications as programs and the data are independent

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

What is data abstraction ( characteristic of data approach)

A

. data storage details hidden and instead user is presented with a conceptual view of data base
. programs refer to data model constructs ( tables , records, objects, relationships) instead of storage details

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

multiple views (second characteristic of data approach)

A

each user can see a different view of data base where only data that is of interest to that user is described

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

What is redundancy

A

Having copies of the same data in different parts of a database

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

How can redundancy lead to problems

A

Every instance of that same data would have to be updated individually rather than just updating it once

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

When to not use a DBMS

A

.When it is too costly:
- ensuring concurrent access/ transactions , security … may be too costly

. when it isnt necessary:
- data is simple or well defined
- single ( or a very limited no of ) users required to access data

. When no DBMS will satisfy:
. real world constrainst like time constrainst that may not be met due to time penalty for using DBMS

. not able to handle complexity of data due to modelling limitations

. special operations required by user that DBMS doesnt support

17
Q

what are data model operations

A

operations used for database updates or retrievals that refer to the constructs ( eg table , entities ,elements) rather than storage details

18
Q

what is the difference between basic - model operations and user defined operations

A

basic model operations are those foundatianal , primitive operations ( Insert , update , delete , select) predefined and already provided by DBMS

whilst user defined are customised operations defined by user for their specific needs

19
Q

give 4 examples of basic model operations

A

select, insert, update , delete

20
Q

Database state

A

The data in the data base AT THAT PARTICULAR MOMENT IN TIME

21
Q

what is database schema

A

The description of a database eg:
. headings of tables, the name of tables ,

.basically descriptions of database structure, data types and constraints on the database

22
Q

Internal schema

A

descibes physical storage structures and access paths

23
Q

conceptual schema

A

describes the structure and constraints of the full database for the whole community of users

  • uses conceptual or implementational data model
24
Q

external schema

A

describes a specific subset of the database for the desired group of users based on their interests ( and so supports multiple views

  • same data model as conceptual schema
25
Q

What does the data definition language (DDL do)

A

. used to specify conceptual schema
. In many DBMS used to define internal and external schema

26
Q

What does the SDL ( storage definition language) do in some DBMS

A

. defines internal and external schema in some DBMS

27
Q

What does DML (data manipulation language) do

A

it specifies the retrieval and update operations

28
Q

How is DML expressed

A

Through general purpose programming languages like java, c , c++ …

OR

through standalone DML commands that are applied directly to database

29
Q

What is a centralised DBMS

A

. combines DBMS , hardware , programs, user interface processing software into a single system

30
Q

Can a user acces centralised DBMS remotely

A

Yes, but centralised DMMS does all the processes

31
Q

Give three example of traditional data models

A

relational , hierachical , network

32
Q

2 examples of emerging

A

object oriented , object relational

33
Q

Homogenous DBMS

A

same DBMS in all sites

34
Q

Heterogenous DBMS

A

Multiple autonomous DBMS connected via a network

35
Q
A

DATABASE SYSTEMS (10 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2024 Bold Learning Solutions. Terms and Conditions