Learning

Aim B

Structured query language (SQL)

Structured query language is a high-level language which is used

to undertake this management activity. In two parts:

1. Data Definition Language (ddl)

This is used top define the database structure

2. Data Manipulation Language (dML)

This is used to add, delete, change and query the data which is held

in the data base structure.

SQL is the language that generates the code used by DBMS.

Content

Acronyms……………………………………………..…………….……………………………………..…....…page 1

RFID………………………………………………………...……………………………………………...…...…...page 2

Roles of server ……………………………………………………………………………………………...…..page 3

Client …………………………………………………….……….…………………………………………..........page4

Bandwidth and Transmission rate …………………………………………………..……..............page4

Router ……………………………………….…………..….………………………………………………....…..page5

How does a search engine work…………………………………………………………….……....…..page 6

Components that make up a URL……………….………………………………...……………....…...page7

Examples of tags used in html code…………………………….………………………………......….page8

Why do tags always come in pairs …………..…...…………………………………...……….……...page9

What is an address book?........................................................................................page10

What are attachments………………………..……………………………………………………….….....page11

What is meant by the term multiple recipients?.....................................................page12

Benefits and drawbacks of email………………………………………………………….………...….page13

Transmission model……………………………………………………………………………..…...……...page 14

Parallel transmission Serial transmission………………………………...…………...…….page15

Universal serial bus………………………………………………………………...………...…..…..page16

Bi-directional transmission…………………………………………….………...…………….…page17

Database and data types……………………………………………………………………….…..page18

Primary key advantages and disadvantages……………………………………………....page19

Relationship between databases ……………………………………………………………….…….page20

Database management software ……………………………………………………………….…...page21

Structured query language ……………………………………………………………………………...page22

Roles of a server

What is a server

A computer or computer program which manages access to a centralized re-

source or service in a network.

What are the roles of a server

Servers often provide essential services across a network,

either to private users inside a large organization or to pub-

lic users via the Internet. Typical computing servers are:

database server- A database server is a computer program that provides data-

base services to other computer programs or computers, as defined by the

client–server model

file server-a device which controls access to separately stored files, as part of a

multi-user system.

mail server, print server ,web server, gaming server, application server

Advantages disadvantages

wireless It is portable and wider

availability.

Wireless connections are

always available

Signal interference

Gives off low level of radia-

tion

broadband Loads quickly and effi-

cient

Unlimited downloading

Not available in rural areas

High monthly fee

Dial up Low cost

Low speed

Unstable dial-up connection

Database management software (DMBS)

Data base management system is the program, which allows you

to create any database that you need and to use the database

that you have created.

Database management system allows you to create, maintain

and search and sort data on a database. It allows different users

to access the database at the same time. It can provide different

levels of access to data .An example of database management

software is Microsoft access.

Relationship between databases

Relationships can be

One to one

An example of where you

might use one to one rela-

tionship is from school to head teacher.

One to many

An example where you might use one to many is mother-

child

Many to many

An example of where you might use many to many rela-

tionship is when students are assigned to courses

Client

What is a client

A client is a desktop computer or workstation that is capable of ob-

taining information and applications from a

server.

A client uses the service of a server. It is not directly attached to the

internet it goes through a internet service provider (IPS).

clients and servers communicate over a computer networkon sepa-

rate hardware, but both client and server may reside in the same

system. A server is a host that is running one or more server pro-

grams which share their resources with clients. A client does not

share any of its resources, but requests a server's content or service

function.

Bandwidth and Transmission rate

Bandwidth

A range of frequencies within a given band, in particular that used

for transmitting a signal.

Transmission rate

A transmission rate is the speed at which a network device com-

municates within the network.

Primary key

A primary key is the unique identifier on each record

in the table The tables may themselves hold fields

which are primary keys in other tables ( foreign keys )

which can be used to access associated information

from many tables in one query.

Foreign key

Primary key

Advantages

The data is sorted and stored easily.

The user can search specific terms e.g. postcode, address.

Take up little physical space

The database can be shred with multiple people

Disadvantages

Unauthorised access to database

A virus could destroy the data

You cant access it if it is malfunction/broken

What is a database?

Database is a system for managing a collection of data. da-

tabase holds data about particular things like name, cus-

tomers or products. It is all stored in a table. The table is

like a grid it holds information about single items which is

also known as a record.

Data types

Text is a sequence of letters numbers and

symbols e.g. someone's name would be in

the format text.

Number it represents a numeric value e.g.

the price of a product.

Date/time stores data or a combination of

dates and times.

Logical represents either yes/no e.g. when

a customer opens an account with a com-

pany ,they might be asked if the service is

good.

Router

What is a router?

A router is a device that forwards data packets between computer networks,

creating an overlay internetwork. A router is connected to two or more data

lines from different networks. When a data packet comes in one of the lines,

the router reads the address information in the packet to determine its ulti-

mate destination.

How is it used?

There are different types of routers :- broadband routers and wireless rout-

ers.

Broadband Routers

Broadband routers can be used to do several different types of things. They

can be used to connect two different computers or to connect two computers

to the Internet. They can also be used to create a phone connection.

Wireless Routers

Wireless routers connect to your modem and create a wireless signal in your

home or office. So, any computer within range can connect to your wireless

router and use your broadband Internet for free. The only way to keep anyone

from connecting to your system is to secure your router.

How does a search engine work?

What is a search engine?

A web search engine is a software system that is designed

to search for information on the World Wide Web. The

search results are generally presented in a line of results

often referred to as search engine results pages.The infor-

mation may be a specialist in web pages, images, infor-

mation and other types of files. It uses bots or rob-bots to

pick up html websites and bring them to the computer

screen .

How is it used ?

When you enter a word or short phrase as a query, the

search engine looks at its index and displays a list of the

‘best matches’, together with a short extract from each

web page. With most general queries there will be many

hundreds or even thousands of matches, so the search en-

gines operate a ranking system for their indexes. The rank-

ing system is used to try to make the results of the search-

es relevant

Client-side processing

is the use of a scripting language to create code on web pages which pro-

vides interactivity. The important point is that the interaction takes place

within the web page and the code is downloaded to the user’s computer

when the web page is opened by the user’s browser. A good example of

a client-side interaction is a roll over (often called a mouseover),

Server-side processing

involves the use of scripts which reside and are run on another com-

puter on the internet . Information is submitted to a server which pro-

cesses it to provide results in the form of a web page. A example of

the submission of a search through a search engine .

Advantages Disadvantages

Client-side processing Speed- works quickly

Security: It is more secure

It can effect the Computer

speed

browser specific not all

scripts work

Server-side processing Efficiency complex code

works efficiency

Browser independent– can

be run on any web browser

Security—can present se-

curity risks

Overloading– server need

large volumes of users.

Bi-directional transmission

About transmitting in both directions. Most recently the

term has been applied to fibre optics. Using the current

technology, light passes in one direction only, so you

have to add extra fibres to the bundle to carry a signal in

the opposite direction.

Both directions

Not through the same wire

What components make up a URL

What does URL stand for Uniform Resource Locator

What does HTML stand for

HTTP = hyper text

transfer protocol.

It is the protocol used

for all data communi-

cation over the world

wide web .

It is an particular

computer on the

internet it is an IP

address

It takes you to an

exact page of the

IP address

Why do tags always come in pairs ?

The first tag in a pair is the start tag, and the second tag is the

end tag. In between these tags web designers can add text, fur-

ther tags, comments and other types of text-based content.

Examples of tags used in html code

<p> paragraph </p>- this tag is used when you want to write a

paragraph you start with <p> and end with <p/>

<h1>heading </h1>- this tag is used when you want to use a

heading. The numbers tell you the size of the heading 1 is the

biggest and 5 is the smallest

<img>- this is used if you want to include an image.

Universal serial bus Universal Serial Bus (USB) is an industry standard developed in

the mid-1990s that defines the cables, connectors and commu-

nications protocols used in a bus for connection, communica-

tion, and power supply between computers and electronic de-

vices. Nowadays USB is used in a wide variety of devices, such

as mobile telephones, memory sticks and MP3 players. USB

ports also supply power to some devices.

USB are on way devices The maximum theoretical transmis-

sion rate for USB 2.0 is 480 Mbps, but this is shared among all

devices on a USB hub, so the rate for each device will be less

than this.

One way

Parallel transmission

Bits of data are transmitted simultaneously over an

equal number of wires or channels. It allows bits of a

whole byte of information to be transmitted together .

It has a short range maximum 5 meters popular for

connecting printers to computers but it is rarely used

these days in computing because of its cost and limited

range .

Serial transmission

bits are transmitted one at a time over a single wire/

channel .This reduces the cost of the cable, but gives a

slower rate of data transfer .In telecommunication, se-

rial communication is the process of sending data one

bit at a time, sequentially, over a communication chan-

nel or computer bus. This is in contrast to parallel com-

munication, where several bits are sent as a whole, on

a link with several parallel channels.

What is an address book?

It stores contacts into an online page with their name, email ad-

dress , phone number e.c.t. when you want to send one of your

contacts a email you can type their name in instead of writing

their full email address.

What are attachments?

An attachment is a computer file sent along with an email mes-

sage. One or more files can be attached to any email message,

and be sent along with it to the recipient. This is typically used as

a simple method to share documents and images. A paper clip

image is the standard image for an attachment in an email client

What is meant by the term multiple recipients

The capability of sending e–mail and instant messages to more than one user at a time by listing more than one e–mail address on a line using semi– colons to separate the email addresses .

Benefits and drawbacks of email

Benefits of email

It is has a quick speed of delivery

Instant delivery on a global scale

Attachments can be sent to recipients

Webmail providers store emails so you can access your

email form anywhere via a web browser

There is no cost to the standard broadband charges

Drawbacks of email

People can hack into your account and read your emails.

Viruses can be sent from one computer to another

Phishing scams

Spam

Email has limitations if the participants are not online at the

same time

Senders and recipients have top have an email account .

Transmission models Simplex transmission :- it sends online data in one direc-

tion . E.g. radio broadcasts.

Half-duplex transmission :- it allows two way communica-

tion but not at the same time. e.g. walkie-talkie

Not at the same time

Full duplex transmission:- it allows to way communication

at the same time .e.g. smart phones