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Best Practice for Data Modelling [message #451959] Mon, 19 April 2010 04:23 Go to next message
lokimisc
Messages: 72
Registered: February 2008
Member
Hi,
I have been assigned a task to analyze the existing data model.
So I would like to know

1. What are the Best Practices to be followed for creating new Data Model ?

2. If existing Data model needs to be analyzed, What are the areas that needs to be given attention?

any suggestion, guidelines are very much appreciated.

Thanks & Regards,
Lokesh
Re: Best Practice for Data Modelling [message #451976 is a reply to message #451959] Mon, 19 April 2010 06:27 Go to previous messageGo to next message
tahpush
Messages: 961
Registered: August 2006
Location: Stockholm/Sweden
Senior Member

1NF, 2NF , 3NF to start with.
Re: Best Practice for Data Modelling [message #451979 is a reply to message #451959] Mon, 19 April 2010 06:45 Go to previous messageGo to next message
Michel Cadot
Messages: 59993
Registered: March 2007
Location: Nanterre, France, http://...
Senior Member
Account Moderator
See normalization.

Regards
Michel
Re: Best Practice for Data Modelling [message #452103 is a reply to message #451979] Tue, 20 April 2010 01:26 Go to previous messageGo to next message
lokimisc
Messages: 72
Registered: February 2008
Member
Thanks Michel & tahpush,

Can you please advise/suggest on below given questions

What is the maximum number of columns a normalized Table can have?

What is the maximum number of foreign key constraint a normalized table can have?

Is it advisable to have a standalone Entity ( Table without any relationship with other table ) in a database ( Er diagram )?
If yes, how much is allowed ?

Thanks & regards,
Lokesh
Re: Best Practice for Data Modelling [message #452105 is a reply to message #452103] Tue, 20 April 2010 01:36 Go to previous messageGo to next message
Michel Cadot
Messages: 59993
Registered: March 2007
Location: Nanterre, France, http://...
Senior Member
Account Moderator
Quote:
What is the maximum number of columns a normalized Table can have?

No maximum in theory, it is the limit the RDBMS allows, but if try to stay as small as possible.

Quote:
What is the maximum number of foreign key constraint a normalized table can have?

No maximum in theory (but the number of combinations of your columns).

Quote:
Is it advisable to have a standalone Entity ( Table without any relationship with other table )

It often happens like parametrization or log tables. They are more technical than functional tables.

Regards
Michel

Re: Best Practice for Data Modelling [message #452320 is a reply to message #452105] Wed, 21 April 2010 05:31 Go to previous messageGo to next message
lokimisc
Messages: 72
Registered: February 2008
Member
Thanks Michel!

Can you please answer below questions also...

1. How to determine the Master Tables and its corresponding Transaction/Child tables looking at ER Diagram?
Is there any tool for doing so?


2. How to identify the mapping (intermediate) table between two master tables eg: Patient and Doctor?


regards,
Lokesh
Re: Best Practice for Data Modelling [message #508704 is a reply to message #452320] Tue, 24 May 2011 02:32 Go to previous messageGo to next message
desertman909y
Messages: 9
Registered: May 2011
Location: dubai
Junior Member
you can start with, try to start 1NF, 2NF , 3NF
Re: Best Practice for Data Modelling [message #522164 is a reply to message #452320] Wed, 07 September 2011 01:33 Go to previous message
Baranor
Messages: 83
Registered: September 2011
Location: Netherlands
Member
lokimisc wrote on Wed, 21 April 2010 05:31
Thanks Michel!

Can you please answer below questions also...

1. How to determine the Master Tables and its corresponding Transaction/Child tables looking at ER Diagram?
Is there any tool for doing so?


2. How to identify the mapping (intermediate) table between two master tables eg: Patient and Doctor?


regards,
Lokesh


Hi Lokesh,

1. For starters on how ERD's work I can reccomend looking at Barker's "Case Method", though somewhat older, the basic notation is still relevant. The crow's foot notation ( see also htt p://en.wikipedia.org/wiki/Entity-relationship_model , crow's foot secion) is commonly used.

2. Write a query based on the foreign key constraints to identify the mapping (see also htt p://www.orafaq.com/forum/t/174532/166871/ ), or follow aliasses, or if al else fails, write query's based on the ID's, counts, and joining ID's, and take a good look at the actual data inside and try to find a logical way to connect them. Of course, the last one can be rather tricky. Good luck!

Regards,

Barry

p.s. this forum won't let me use links till I've posted more than 5 messages... so you'll have to remove the extra space from the links yourself, just copy paste.
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