VCE IT Helpdesk

[excal]

Feel free to ask any queries you have about any IT subject's coursework in the lead up to the exams - this can be questions about the content itself or explanations regarding trial exam questions.

This is for both IT:A and IT:SD.

I will edit this post with questions and best answers as it arises.

Databases

input masks - are used when you want people to enter data is a specific way. This restricts them from entering data that is not needed. commonly used with telephones and post codes.

primary key - unique identification of a particular ROW. When linking with another table, you must have a unique primary key (hence the word unique, and the "1", because there is only one). The infinity symbol is where you have more than one columns which you can relate to.

linking table - refer to this post. These are used only to implement many-to-many relationships in a database.

Data type for phone numbers - phone numbers should be text as they can have () for area codes. Also with numeric, it means they are numbers and thus we could do some statstical work on the data in the records. Don't think we want to do that with a mobile number.

[Noblesse]

Great idea Excalibur, tomorrow afternoon I'll edit this post and add some questions!

[droodles]

i'm looking for the coffee machine, do you know where it is?

[RD]

I suck at databases. What's the purpose of an input mask and primary key? and what does it mean when they have like a link which has 1 and an infinity logo. (one to many or w/e.)

[transgression]

input masks = is used when you want people to enter data is a specific way. This restricts them from entering data that is not needed. commonly used with telephones and post codes

primary key = unique identification of a particular ROW. When linking with another table, you must have a unique primary key (hence the word unique, and the "1", because there is only one). The infinity symbol is where you have more than one columns which you can relate to.

Ie. Borrowing dvds from a store
You have a unique DVD_ID, which in turn, may link with many dvds you borrow (infinity), and our Borrower_ID (unique)

[ell]

primary key = unique identification of a particular column.

Generally the primary key uniquely identifies a particular row. (unless you've put your records in the columns instead of the rows, which is a bit odd!)

[transgression]

fixed, thanks ell

[excal]

primary key = unique identification of a particular column.

Generally the primary key uniquely identifies a particular row. (unless you've put your records in the columns instead of the rows, which is a bit odd!)

Well, you could take it a bit further and say that a primary key DOES uniquely identify each row. It simply has to by design.

Note that more than one field can be grouped together to be a primary key - this is known as a composite (primary) key.

[excal]

input masks = is used when you want people to enter data is a specific way. This restricts them from entering data that is not needed. commonly used with telephones and post codes

primary key = unique identification of a particular ROW. When linking with another table, you must have a unique primary key (hence the word unique, and the "1", because there is only one). The infinity symbol is where you have more than one columns which you can relate to.

Ie. Borrowing dvds from a store
You have a unique DVD_ID, which in turn, may link with many dvds you borrow (infinity), and our Borrower_ID (unique)

He's talking about two different things. You've answered the primary key aspect of it, but the other thing he refers to is relations (or relationships in Access parlance).

These consider how the databases (consider them as 'entities' or 'things') are related to each other. Consider a simple classroom database:

- For each Class, there will be one teacher. For each teacher, they could be running more than one class. Therefore, 1:1 + 1:m = one:many
- For each Class, there is more than one student. For each student, they have more than one class. Therefore, 1:m + m:1 = many:many

(for many to many, you will need a linking table - has someone taught you this?)

[RD]

(for many to many, you will need a linking table - has someone taught you this?)

hell no, stupid teacher didn't teach my class shit.

[Glockmeister]

I dont' actually think that linking tables are part of the course...

[jsimmo]

I dont' actually think that linking tables are part of the course...

yeah it is. i'm pretty sure there was a question on last years exam where you had to identify the correct data structure diagram that had the correct positions of the one to many symbols.

I think maybe it comes under the 'structure of databases' dot point in the study design?? not sure

[Glockmeister]

That's not really a linking table though...

A linking table is what you would use if you have a many to many relationship so that between each table, there will be a one of many relationship, since you can't link many to many relationships together.

[excal]

That's not really a linking table though...

A linking table is what you would use if you have a many to many relationship so that between each table, there will be a one of many relationship, since you can't link many to many relationships together.

IIRC, it was a linking table.

[Glockmeister]

ah serious? oh ok.