[Year 12 IT Apps] Database relationships

Fri Jul 25 10:59:00 EST 2008

Hi Jim.  If you're not a teacher, would you mind saying where you 
are/what you do/why you're here?

Relationships are great fun, and source of endless debate amongst 
people.  I think database structures border on works of creative art, 
sometimes.

It's a sad sign that I sometimes lie awake at night pondering complex 
relationships that involve key fields instead of women

:-(

Jim Maunder wrote:
> Don't know if this will help:
> 
> I'm not even a teacher let alone an IPM teacher - but I have fiddled 
> with databases in my chequered past and remember something about 3rd 
> normal form from the Grad Dip Comp course 20 odd years ago. I set up a 
> quick sample in Access to show how I would go about a student database:
> 
> Emacs!
> 
> I would say that students and form have a 1 to 1 relationship, and that 
> students and stud_subj has a 1 to many relationship, but I'm only guessing.
> 
> rgds
> Jim
> 
> 
> 
> At 05:25 PM 24/07/2008, you wrote:
>> Yes it is confusing but I would still argue that it is one entity and 
>> that entity has a number of data relationships in it. There is also 
>> only one Medicare card number on it and that is unique – each child 
>> does not get their own Medicare card with a different Medicare number.
>>  
>>  
>>  
>>  
>> Kind regards
>>  
>> Allan Barnes, CEO
>> Australian Institute of Education and Training
>> P.O. Box 171
>> Brunswick West 3055
>> Ph: (03) 9387 2051
>> FAX: (03) 9387 3470
>> Mobile: 0409 428 221
>>  
>>  
>> *From:* itapps-bounces at edulists.com.au [ 
>> mailto:itapps-bounces at edulists.com.au] *On Behalf Of *Russo, Frank R
>> *Sent:* Thursday, 24 July 2008 8:33 AM
>> *To:* Year 12 IT Applications Teachers' Mailing List
>> *Subject:* RE: [Year 12 IT Apps] Database relationships
>>  
>> Sorry but a medicare card can have multiple members in it but each 
>> member can have their own card !!!
>>  
>> Now that’s confusing………..
>>  
>> Frank Russo
>> ICT ~ Teaching & Learning
>> Monterey Secondary College
>> ------------------------------------------------------------------------
>> *From:* itapps-bounces at edulists.com.au [ 
>> mailto:itapps-bounces at edulists.com.au] *On Behalf Of *Allan Barnes
>> *Sent:* Wednesday, 23 July 2008 9:14 PM
>> *To:* 'Year 12 IT Applications Teachers' Mailing List'
>> *Subject:* RE: [Year 12 IT Apps] Database relationships
>>  
>> An example of a one-to-one relationship would be something like a 
>> ‘person’ entity and a ‘medicare card’ entity – one person can only 
>> have one medicare card, and one medicare card can only belong to one 
>> person.
>>  
>>  
>>  
>>  
>>  
>> Kind regards
>>  
>> Allan Barnes, CEO
>> Australian Institute of Education and Training
>> P.O. Box 171
>> Brunswick West 3055
>> Ph: (03) 9387 2051
>> FAX: (03) 9387 3470
>> Mobile: 0409 428 221
>> *From:* itapps-bounces at edulists.com.au [ 
>> mailto:itapps-bounces at edulists.com.au] *On Behalf Of *Mia Alexiou
>> *Sent:* Wednesday, 23 July 2008 9:05 PM
>> *To:* Year 12 IT Applications Teachers' Mailing List
>> *Subject:* Re: [Year 12 IT Apps] Database relationships
>>  
>> Hi all,
>>
>> I'm an intruder here (I tech year 11 not year 12) but I thought I 
>> could share my somewhat rusty knowledge of databases.
>>
>> In response to Lisa's question the employee/department relationship is 
>> one-to-many.   As for "true" one-to-one relationships I've never seen 
>> one in action and so doubt they are common at a small database level.  
>> That being said, I can think of a couple of situations where they 
>> might be useful such as splitting commonly needed data from that which 
>> is rarely needed, to reduce the time it takes to run queries over a 
>> huge table.  Another reason might be security, with highly sensitive 
>> data being stored in a separate table.
>>
>> A 0 or 1 to-many relationship is much more common and is what most 
>> people (even in industry) usually mean when they talk about one-to-one 
>> relationships.  These are explained nicely (under the one-to-one 
>> heading!) at http://www.onlamp.com/pub/a/onlamp/2001/03/20/aboutSQL.html.
>>
>> I hope this was helpful
>>
>> Mia Alexiou
>> RMIT TAFE
>> Information Technology
>> Sessional Teacher
>> On Wed, Jul 23, 2008 at 6:10 PM, Lisa Imms <lisimms at copticvic.org 
>> <mailto:lisimms at copticvic.org>> 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 
>> <mailto: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 <http://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?
>> _______________________________________________
>> http://www.edulists.com.au < http://www.edulists.com.au/>  - FAQ, 
>> resources, subscribe, unsubscribe
>> IT Applications Mailing List kindly supported by
>> http://www.vcaa.vic.edu.au/vce/studies/infotech/itapplications3-4.html 
>> - Victorian Curriculum and Assessment Authority and
>> http://www.vitta.org.au < http://www.vitta.org.au/>   - VITTA 
>> Victorian Information Technology Teachers Association Inc
>>
>> _______________________________________________
>> http://www.edulists.com.au - FAQ, resources, subscribe, unsubscribe
>> IT Applications Mailing List kindly supported by
>> http://www.vcaa.vic.edu.au/vce/studies/infotech/itapplications3-4.html 
>> - Victorian Curriculum and Assessment Authority and
>> http://www.vitta.org.au  - VITTA Victorian Information Technology 
>> Teachers Association Inc
>>  
>> _______________________________________________
>> http://www.edulists.com.au <http://www.edulists.com.au>- FAQ, 
>> resources, subscribe, unsubscribe
>> IT Applications Mailing List kindly supported by
>> http://www.vcaa.vic.edu.au/vce/studies/infotech/infotechindex.html 
>> <http://www.vcaa.vic.edu.au/vce/studies/infotech/itapplications3-4.html%20>- 
>> Victorian Curriculum and Assessment Authority and
>> http://www.vitta.org.au <http://www.vitta.org.au>- VITTA Victorian 
>> Information Technology Teachers Association Inc
>>  
>>
>> Message protected by MailGuard: e-mail anti-virus, anti-spam and 
>> content filtering.
>> http://www.mailguard.com.au/mg
>>
>> Report this message as spam 
>> <https://login.mailguard.com.au/report/1vuYjlI9hA/408s2xedFO3BSztpPnlZPi/0.004>  
>>
>>  
>>
>> No virus found in this incoming message.
>> Checked by AVG - http://www.avg.com <http://www.avg.com/>
>> Version: 8.0.138 / Virus Database: 270.5.4/1567 - Release Date: 
>> 7/22/2008 4:05 PM
>> _______________________________________________
>> http://www.edulists.com.au <http://www.edulists.com.au>- FAQ, 
>> resources, subscribe, unsubscribe
>> IT Applications Mailing List kindly supported by
>> http://www.vcaa.vic.edu.au/vce/studies/infotech/infotechindex.html 
>> <http://www.vcaa.vic.edu.au/vce/studies/infotech/itapplications3-4.html%20>- 
>> Victorian Curriculum and Assessment Authority and
>> http://www.vitta.org.au <http://www.vitta.org.au>- VITTA Victorian 
>> Information Technology Teachers Association Inc
>>
>> *Important - *This email and any attachments may be confidential. If 
>> received in error, please contact us and delete all copies. Before 
>> opening or using attachments check them for viruses and defects. 
>> Regardless of any loss, damage or consequence, whether caused by the 
>> negligence of the sender or not, resulting directly or indirectly from 
>> the use of any attached files our liability is limited to resupplying 
>> any affected attachments. Any representations or opinions expressed 
>> are those of the individual sender, and not necessarily those of the 
>> Department of Education and Early Childhood Development.
>> _______________________________________________
>> http://www.edulists.com.au <http://www.edulists.com.au>- FAQ, 
>> resources, subscribe, unsubscribe
>> IT Applications Mailing List kindly supported by
>> http://www.vcaa.vic.edu.au/vce/studies/infotech/infotechindex.html 
>> <http://www.vcaa.vic.edu.au/vce/studies/infotech/itapplications3-4.html%20>- 
>> Victorian Curriculum and Assessment Authority and
>> http://www.vitta.org.au <http://www.vitta.org.au>- VITTA Victorian 
>> Information Technology Teachers Association Inc
>>  
>>
>> Message protected by MailGuard: e-mail anti-virus, anti-spam and 
>> content filtering.
>> http://www.mailguard.com.au/mg
>>
>> Report this message as spam 
>> <https://login.mailguard.com.au/report/1vvb6j8dnF/30VxZzeOF4ZuSaw7vMDc47/0.002>  
>>
>>  
>>
>> No virus found in this incoming message.
>> Checked by AVG - http://www.avg.com <http://www.avg.com/>
>> Version: 8.0.138 / Virus Database: 270.5.4/1567 - Release Date: 
>> 7/22/2008 4:05 PM
>> _______________________________________________
>> http://www.edulists.com.au <http://www.edulists.com.au>- FAQ, 
>> resources, subscribe, unsubscribe
>> IT Applications Mailing List kindly supported by
>> http://www.vcaa.vic.edu.au/vce/studies/infotech/infotechindex.html 
>> <http://www.vcaa.vic.edu.au/vce/studies/infotech/itapplications3-4.html>- 
>> Victorian Curriculum and Assessment Authority and
>> http://www.vitta.org.au <http://www.vitta.org.au>- VITTA Victorian 
>> Information Technology Teachers Association Inc
>> No virus found in this incoming message.
>> Checked by AVG -
>> http://www.avg.com <http://www.avg.com/> 
>> Version: 8.0.138 / Virus Database: 270.5.5/1570 - Release Date: 7/24/2008
>> 6:59 AM
> 
> 
> -----------------------------------------------------------
> We have to use this Disclaimer
> 
> This message, including any attachments, is provided without
> responsibility in law for its accuracy or otherwise and without
> assumption of a duty of care by the School. Whilst every attempt has
> been made to ensure material in this email message is free from
> computer viruses or other defects, the attached files are provided,
> and may only be used, on the basis that the user assumes all
> responsibility for use of the material transmitted. This email is
> intended for the use of the named individual or entity and may
> contain confidential and privileged information. Any dissemination,
> distribution or copying by anyone other than the intended recipient
> of this email is strictly prohibited. If this email has been
> received in error, then please notify Ruyton Girls' School
> immediately and destroy the original message.
> 
> Views, opinions, etc. expressed reflect those of the author and not
> Ruyton Girls' School
> -----------------------------------------------------------
> 
> Jim Maunder
> Laptop and PC Support Technician
> Ruyton Girls School
> Melbourne, Australia
> ph 03 9290 9374
> 
> _______________________________________________
> http://www.edulists.com.au <http://www.edulists.com.au> - FAQ, 
> resources, subscribe, unsubscribe
> IT Applications Mailing List kindly supported by
> http://www.vcaa.vic.edu.au/vce/studies/infotech/infotechindex.html 
> <http://www.vcaa.vic.edu.au/vce/studies/infotech/itapplications3-4.html 
>  > - Victorian Curriculum and Assessment Authority and
> http://www.vitta.org.au <http://www.vitta.org.au> - VITTA Victorian 
> Information Technology Teachers Association Inc
> 

-- 
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?