| Best Practice for Data Modelling [message #451959] |
Mon, 19 April 2010 04:23  |
lokimisc
Messages: 101
Registered: February 2008
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Senior Member |
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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
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| Re: Best Practice for Data Modelling [message #452103 is a reply to message #451979] |
Tue, 20 April 2010 01:26  |
lokimisc
Messages: 101
Registered: February 2008
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Senior Member |
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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
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| Re: Best Practice for Data Modelling [message #452320 is a reply to message #452105] |
Wed, 21 April 2010 05:31 |
lokimisc
Messages: 101
Registered: February 2008
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Senior Member |
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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
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| Re: Best Practice for Data Modelling [message #522164 is a reply to message #452320] |
Wed, 07 September 2011 01:33 |
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Baranor
Messages: 83
Registered: September 2011
Location: Netherlands
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Member |
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lokimisc wrote on Wed, 21 April 2010 05:31Thanks 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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