[Year 12 IT Apps] Database relationships

[Mark Kelly]

O bother.  Apologies. That map didn't finish up too well.  For what it's 
worth, the proper version is attached.

Mark Kelly wrote:
> Hi Lisa. Firstly please don't be afraid to challenge me.  I'm far from 
> infallible. In fact I remember  making a mistake at some time.  It was 
> in 1983, I believe...
> 
> I agree with you: the example I gave for 1:1 was not good.  I should 
> have used a real-life example like ones below, but I was trying to keep 
> a certain similarity between the examples in the handout.
> 
> Anyway, I see a one-to-one relationship basically like VLOOKUP in Excel. 
> They can be vital, and don't, I believe, they necessarily point to 
> structural deficiency.
> 
> Fregzample... in my reporting database ('Rupert') the teacher selects 
> the subject to be reported on in one table (where the reports are 
> created).  There is a one-to-one relationship between the subject 
> selected in that table (rupert.fp7) and the same subject ID in the 
> subjects table (subjects.fp7) from which all the subject information 
> (full name, assessment tasks, task weightings, VELS dimensions, 
> outcomes) are stored.
> 
> Similarly, when a student is selected in rupert.fp7, his/her info (full 
> name, form, registration #, sex etc) is drawn from students.fp7 into the 
> report.
> 
> The full relationship map of Rupert is attached.  I'm sure it could be 
> more efficient, but every time I try radically rebuilding it, I spend a 
> week re-learning why I did it that way, changing small things and end up 
> breaking everything.  So I now tend to leave it alone :-)
> 
> Thanks for the heads-up, Lisa.  I'll amend my handout.
> 
> Cheers
> Mark
> 
> Lisa Imms wrote:
>> Hi Mark,
>>  
>> Firstly, thanks for the resource :-)
>>  
>> I hate to even contemplate disagreeing with you as my ITA class and I 
>> regard you as the ITA font-of-all-knowledge, but I will try this 
>> anyway.....
>>  
>> Your example for one-to-one: "E.g. an employee's department data in 
>> one table matches a corresponding department in another table, 
>> allowing data relating to that department to be fetched."
>>  
>> Wouldn't this be a one to many relationship? Even the line you have 
>> joining them has the 'many feathers' at the employees table? Although 
>> each employee can belong to only one department, each department can 
>> (and will) have multiple employees? So it is actually a one to many 
>> relationship?  
>> Am I correct in assuming that a well organised database would not have 
>> any one-to-one relationships? The two tables in a one-to-one 
>> relationship could/should just be merged into one table?  
>> Lisa Bairstow
>> St Mary's Coptic Orthodox College
>>
>> ________________________________
>>
>> From: itapps-bounces at edulists.com.au on behalf of Mark Kelly
>> Sent: Wed 7/23/2008 2:24 PM
>> To: Year 12 IT Applications Teachers' Mailing List
>> Subject: [Year 12 IT Apps] Database relationships
>>
>>
>>
>> Hi all.  It's been mighty quiet here for a while.  To perk things up,
>> here's a little revision for database relationships (1-1, 1-many,
>> many-many) that may or may not be useful.
>>
>> Cheers
>> Mark
>>
>> -- 
>> Mark Kelly
>> Manager - Information Systems
>> McKinnon Secondary College
>> McKinnon Rd McKinnon 3204, Victoria, Australia
>> Direct line / Voicemail: 8520 9085
>> School Phone +613 8520 9000
>> School Fax +613 95789253
>> kel AT mckinnonsc.vic.edu.au
>>
>> Webmaster - http://www.mckinnonsc.vic.edu.au 
>> <http://www.mckinnonsc.vic.edu.au/> IT Lecture notes: http://vceit.com 
>> <http://vceit.com/> Moderator: IT Applications Mailing List
>>
>> If you Declare War - is it integer or boolean?
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> 
> 
> 
> ------------------------------------------------------------------------
> 


-- 
Mark Kelly
Manager - Information Systems
McKinnon Secondary College
McKinnon Rd McKinnon 3204, Victoria, Australia
Direct line / Voicemail: 8520 9085
School Phone +613 8520 9000
School Fax +613 95789253
kel AT mckinnonsc.vic.edu.au

Webmaster - http://www.mckinnonsc.vic.edu.au
IT Lecture notes: http://vceit.com
Moderator: IT Applications Mailing List

A conclusion is the place where you got sick of thinking.
If you Declare War - is it integer or boolean?
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