Entities
Aug 24, 2006
Can people give their thoughts on the following sernario.
When I have been taught database design in the past it has always been with the aid of examples that have very distinct entities. For example: People loan copies of books.
For the sake of simplicity say you have a booking system.
Event(EventID, EventName, EventDate)
Person(PersonID, Firstname, Surname, ... Postcode)
Booking(BookingID, Person, Event, Guests)
This is the same level of simplicity. However I have never been shown an example where the person entity is more specialised.
What if a database needs to hold details on people of different types? Say you hold college students, school techers and business owners. The details that is required on each is:
Student(Firstname, Surname, College, Address, DOB)
Teacher(Firstname, Surname, School, JobTitle)
BusinessOwner(Firstname, Surname, Business)
I assume that this requires three tables as appose to the one Person table but how does the booking relationship work?
How would you link Events to perople of all three types?
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Jul 17, 2005
Hi
First off I want to say I have tried to answer thsi for myself, I have a number of books and I have looked there for the answer, but not sure whether I am understanding it all properly, perhaps I am making it more complicated than I need to :confused:
I want to design a simple database for keeping track of an audit I do monthly at work. I have made sense of the following:
1. I know for sure that I have 2 entities for sure, PrimaryNurse and Patient;
2. I know that each PrimaryNurse is "PrimaryNurse" to 1 or more Patients;
3. I know that each Patient has 1 and only 1 PrimaryNurse;
What I am not sure about is whether the items I audit (they are all to do with the patient, for example is there a photo of them in their clinical file, have they had their legal rights read to them, etc) are to remain in the Patient Table as simple "yes/No" or to be moved to a table of there own.
I apologise if this is yet another simple question for those of you who already understand. If you could shed some light on this that would be great as I want to learn as opposed to just asking for answers.
Thanks
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Apr 20, 2005
Hi,
I am designing a database.
It is going to store data from questionnaires.
The natural way seems to be to have a table - that stores where the data comes from, what is it about, what is the question and what is the answer, like this:
DataProviderID; FocusID; QuestionID; AnswerValue
My problem is that a Focus could be a eg. a Person, a Company or a Job - meaning that somebody may be giving info on an other person, on a Company or on a Job.
Now Persons, Companies and Jobs would have very different properties.
So how should I solve this shold I have a common table for Peoples, Companies and Jobs and use a very complicated structure of properties for them or should I store these entities in separate tables but than how will I store the results?
Thanks for your thoughts.
SWK
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Sep 6, 2006
Hi
i currently have a simple spreadsheet in Excel containgin the following fields.
## Date - not unique
simpy shows the date of the transaction
## Debt - who the debt will be paid to - unique per date (e.g. CompanyA)
## Type of debt - what service is it - not unique by date or debtor (e.g. Wages)
## Net Price before VAT (X)
## VAT (value added tax, a UK tax) (Y)
## Price of Service (Z = X+Y)
## Running total of Net Price before VAT (X + X + X...)
## Running total of VAT (Y + Y + Y...)
##Balance - (Z + Z + Z...)
The spreadsheet currently calculates this automatically using simple formulas.
I'd like to create a nice little interface for this data entry using MS access forms. From then I can easily create queries and reports etc.
can somebody please help me out! :D I've tried to list my entities and create an ERD to no avail!
Many Thanks
Mike
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Sep 21, 2004
hi friends,
i have tried had to connect sub type tabels (Saving, Checking, Loan... they have their own ids...) with super type (Account...it has account id...) on the condition of account_type (either "S","C" or "L") attribute in ACCOUNT entity.
how to joint them??? with query or with expression??
i expect help from you.........please.
........thanks.
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