Syllabus Detail
- Data manipulation. 12 ATAR
Background
- To manipulate data means to change or process information
- Data can be manipulated in order to make it easier to read, to organize certain elements or to change the information completely
- The manipulation of data is common in applications such as websites, where data is concurrently being selected and updated, or even inserted or deleted
- Data manipulation langauges (DML's) such as SQL are utilised to manipulate data from sources such as databases
Common DML Commands
- SELECT: This command is used to ouput a list of rows (or record) from a database.
- Syntax: SELECT [x] FROM [y] WHERE [z]
- UPDATE: This command is used to alter the data from one or more tables.
- Syntax: UPDATE [x] SET [y] WHERE [z]
- INSERT: This command is used to add one or more entries to a database table.
- Syntax: INSERT INTO [x] [y] VALUES [z]
- DELETE: This command removes one or more entries from a database table depending on the conditions.
- Syntax: DELETE FROM [y] WHERE [z]
Further Research
Worksheet and Practice (yet to be added)
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Syllabus Detail
- Data duplication. 12 ATAR
- Data redundancy. 11 ATAR, 12 GEN, 12 ATAR
Background
- Data duplication and data redundancy are similar concepts, but are not the same
- Both concepts work to ensure efficiency and consistency in terms of databases and storage
Data Redundancy
- Data redundancy occurs when the same data is entered in to two or more fields of a database
- For example, "Joe" is entered in to the Name field under a record called Customers
- "Joe" is also entered in to the Customer field under a record called Purchases
- Although we are referring to the same Joe in both fields, each piece of data is seen as unique
- This means that to update "Joe", we need to manually edit each reference
- This can cause problems in database systems such as data anomalies
- This differs from data duplication, as it is often not intentional and can take up potentially required storage space
Data Duplication
- Data duplication occurs when an exact copy of a piece of data is created
- For example, copy and pasting an item called "MyPicture.jpg"
- The new pasted item contains the exact same data as the original picture
- On different Operating Systems, the naming convention for copies will change (e.g. "MyPicture 2.jpg" or "MyPicture copy.jpg")
- Data duplication provides benefits such as providing us with the ability to back up copies of files and create multiple verions of a file (which may be required for progress reporting or other information)
- The duplication of data is often intentional and used primarily for creating backups
- Data duplication on a database may result in data redundancy, and thus an inefficient and inconsistant database
Why are these important?
- The act of normalising a database (organizing data to prevent redundancy) is critical to maintain an efficient and clean database
- Ensuring unncessary data doesn't reside on the database allows for a consistent and accurate database
- The ability to duplicate data intentionally allows us to create backups and maintain our data
Further Research
- Read more about Data Redundancy from DatabaseDev here
- Read more about Data Duplication from GeekInterview here
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Syllabus Detail
- Data security 12 ATAR
Background
- Data security refers to protecting data (or information) from unwanted or unauthorized actions from potentially harmful users
- This applies to computer access, databases and all types of personal information
- Data security is an integral part of the IT industry as it helps to ensure the security and privacy of sensitive information
Why do we need to secure our data?
- Data security is essential to protect privacy of individuals
- It is also essential to protect intellectual property of individuals, businesses or governement
- Data is very attractive to criminals as data theft can lead to bank fraud or other illegal financial gain
- Data security can also help to prevent malicious attacks on a computer system
- To use the security practice of restoring from back ups to retrieve data when corruption occurs
Tips for securing data
- Place data servers in locked rooms to prevent physical access and theft
- Use strong passwords on network devices to prevent access to data
- Physically lock away any sensitive information on an external drive
- Enable a firewall and restrictions on Internet access
- Use an anti-malware program such as MalwareBytes and ensure it is up to date
- Use an anti-virus program and ensure it is up to date
- Secure your WiFi network with a passphrase to ensure no unauthorized access to your local network
- Activate password protection for devices to lock out unwanted guests
- Regularly backup data to separate devices and store off site with password protected copies
Further Research
- Read some more tips on data security by SpamLaws here
- Read 10 ways to secure your data on Computer World here
Worksheet and Practice (yet to be added)
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Syllabus Detail
- Database terms; data, field, record, relation, atomicity 11ATAR, 12 GEN
What are Database Terms?
- A database is a structured set of data held within a computer
- A term is a word or phrase used to describe something or express a concept
- A database term is simply a word used to define aspects of a database
Term: "Data"
- In terms of computing, data can be seen as quantities, characters or symbols
- A computer is then able to perform operations on these items known as data
- In a database, data refers to the values of which are stored within the database structure
Term: "Field"
- A field is the smallest unit of information that can be accessed from within a database
- Fields can also be seen as columns, as the title of each field makes up the column's name
- Database tables are made up of columns and rows consisting of fields that hold a value
Term: "Record or row"
- A record is a group of fields in a database that are related to one entry
- A record can also be seen as a row
- Remember: records (or rows) follow a horizontal path
Term: "Relation"
- The word relation is used interchangeably with the word table
- They both provide information about an entity in a database
- Examples of these would be; customer, order, product,
- It was created by E.F Codd the father of relational databases
- It goes with tuples (rows), which have attributes (columns) to make up a relation (table). see wikipedia
Term: "Atomicity"
- a system that allows you conduct a full transaction, or no transaction at all.
- this needs to happen for booking air tickets, tranferring money on the internet.
- it is an atom metaphor, you can't divide the transaction, it all works, or it all does'nt work.
- atomicity explained here http://beginnersbook.com/2015/04/acid-properties-in-dbms/
- atomicity is to ensure it all works, or it doesn't work.
- This a good thing, If you are transferring money to pay a bill or to give to someone. You don't want to be stuck halfway wondering whether it went through or not.
- It can do this by monitoring the transaction. Read > Copy > Update.
- If a system crashes, it ignores incomplete transactions.
For you to do
- Place these terms in order from largest to smallest; field, entity, attribute
- Match the interchangeable words table, row, column, relation, tuple, attribute
Further Research
- Highy recommended for more about databases here
- View an extensive list of Database Terms from Raima here
- Read more about Database Terminology from About.com here
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