Steph 2011

Thursday, March 10, 2011

HSC - 2008 +2009

2008: question 21:a)

PETS context diagrams.

b). Owner telephone number: texting is used as no calculations are required within that fields
Paid: boolean is an efficient choice to determine whether the customer has paid the fees or not, as it has only two possible choices.
c). Create another table and link it to the original table where the customers details are recorded. by creating a new field in the original table such as a VET ID will link the vet's details who implanted the microchip to the customer.

Question 22.

a).training staff:

Monday, March 7, 2011

Term 1 Week 6 - Searching, Selecting and Storing (178-190)

* - represents multiple function in a database

relational operator: > < = => <=
logical operators: and or not
order by :

SQL Syntax:

Define: (162-169)
Data independance: type of data transperancy that matters for a centralised DBMS. Seperation of data from the programs that manipulate data.
concepts of data independace: data is independant from system

Direct and Sequential access: Direct : refers to the ability to go to any data item in any order. Once the location of the required data is known then that data can be read or written directly without accessing or affecting any other data.
e.g. hardisks, usb's

Sequential: means the data must be stored and retrieved in a linear sequence. the tiemt aken to locate data makes sequential storage unsuitable for most application apart from backup
e.g. audio/video tape

On-line Storage: available immediately to connected computers. includes hard disks within a single computer and also storage devices accessed via a network or even over the internet. usually in the form of hard disk drivers. online storage over the net is becomming more common.

Off-line Storage: refers to data stored such that it cannot be accessed until the storage media is mounted into a driver. eg. magnetic tape, optical media such as CD's and DVD's and USB's

Magnetic Storage: provides large storage capacity and in the case of hard disks, it allowd for direct access at high speed for both storing and retrieving process.
- head moves fractions of seconds above the plate

e.g hard disks, tapes, floppy disks,

*Basic understanding of storage media: magnetic, optical, hard disk, RAID and tape

Hardware - Storage.
Hard Disks: store data magnetically on precision aluminium of glass platters. the platters have a layer of hard magnetic material into which the magnetic data is stored. each platter is double sided, so two read/write heads are required for each platter contained within the drive's casing.

RAID: utilises multiple hard disk drives together with a RAID controller. it controller manages the data flowing between the hard disks and the attached computer; the attached computer just sees teh RAID device as a normal single hard disk. stirping data across multiple drives improves speed.
RAID level 1: mirroring data
RADI level 5: parady data seperated into multiple disk drives

Blu Ray discs: have a larger storage capacity because the frequency of light is in the blue region, and not the red region like in other DVDs, although they are the same size.
The higher the frequency of the laser, the more depths the data can be packed on the surface of the disk. Data can be more densely packed on the surface of the disk

1. ProductID of products costing more than $10:
Select.InvoiceProducts.ProductID,InvoiceProducts.InvoiceCosts
From.InvoiceProducts
Where.InvoiceProducts.InvoiceCosts>10
Orderby.

2. Invoice numbers of invoices placed on 09/06/06
Select.
From.
Where.
Orderby.

Wednesday, March 2, 2011

HTML

basic page will have html tag at the start and end

<html>

<head>

general formating instructions: e.g. fonts, background colours,
css - cascading style sheets

</head>

<body>

content

</body>

</html>

Normalisation: pg 149 (1-11)

Monday, February 28, 2011

Hypertext, Logical Organisation and Stordyboards

Hypertext (Hypermedia): term used to describe bodies of text that are linked in a nonsequential manner. the related term hypermedia is an extension of hypertext to include links to a variety of different media types including image, sound and video. (text that link to other blocks of texts)

The Logical organisation of hyptertext/Hypermedia: based on links (hyperlinks) and nodes. a set of nodes and their various links form a web - e.g. www.

Node: a point where links are connected. in a computer network a node is a device connected to the network. in hypertext terms node is usually some block or unit of information.

Storyboards: technique that was first used for the creation of video infromation, includign film, television and animation.

shows the various interfaces (screens)
to identify the purpose, contents and design elements
should identify area's used fro input, output and nagitaional elements.

4 Types of Storyboards:

Linear navigation: one single path -> simple to navigate, but not very flexible must go through each board before reaching a specified one

Hierarchical navigation: particularly suited to information that falls into categories and sub categories. once in a particular category, users are not overwhelmed by information from other categories, to navigate into another category user must move back up the hierarchy and then select another path.

Non-Linear navigation: difficult to visualise. allows maximum flexibility of design, but is easy for a user to get lost in a maze of screens. if a non linear structure is used in most cases some form of map is also provided.
e.g games

Composite: combines aspect of each of the other structures. in reality most hypertext webs use composite structure. makes sense as most web include instructional nodes that form a sequence, together with informational nodes that have some form of inherent classification.

Wednesday, February 23, 2011

Normalising Databases

Normalising: getting rid of redundant data
if there is redundant data:

takes up too much space
if one needs to be edited than all will required to be edited
creates maintainence problems

Normalisation process is theorectically by progressional decomposing design into a sequence of normal forms - first, second and third.

First Normal Form (1NF):

deals with the removal of repeating attributes across horizontal rows abnd ensures each field holds single data items.
each field stores single data
no multiple data items within individual fields and no fields are repeated

Second Normal Form (2NF)

removes redundant data within verticle columns ro fields
all tables must be in first normal form
every non-key attribute is funtionally dependant on the table's primary key - but not unique (primary key defines the attribute + identifies the non key attribute - functionallt dependant)
e.g date of birth, address and phone number are functionaly dependant on student ID

Third Normal Form (3NF)

removes furyher redundant data within vertical columns or fields
all tables must be in second normal form
every non-key attribute is functionally dependant only on teh table's primary key and not on any other attributes of the table.
e.g. Kmart Layby! -> Layby no. -> phone number, suburb, surname -> functionally dependant on customer details

Monday, February 14, 2011

T1 Week 3: Relational Databases

http://bettscomputers.com/moodle/course/view.php?id=26&topic=all

Primary Key: Composite key - they are unique fields
Foreign Key: e.g The foreign keys generally define parent-to-child relationships between tables.

Database for School Library Loans