SQL Server Forums
Profile | Register | Active Topics | Members | Search | Forum FAQ
 
Register Now and get your question answered!
Username:
Password:
Save Password
Forgot your Password?

 All Forums
 General SQL Server Forums
 New to SQL Server Administration
 ERD and Table
 New Topic  Reply to Topic
 Printer Friendly
Author Previous Topic Topic Next Topic  

wahidullah
Starting Member

Afghanistan
5 Posts

Posted - 05/15/2013 :  08:14:32  Show Profile  Reply with Quote
Hi, while developing a database, Is it necessary to create the number of tables equal to the number of entities?

thanks!

wahidullah290

visakh16
Very Important crosS Applying yaK Herder

India
52317 Posts

Posted - 05/16/2013 :  00:41:31  Show Profile  Reply with Quote
nope. Although most cases there will be 1-to -1 mapping. There can be cases where entity can be broken up into multiple tables when applying normalisation etc

------------------------------------------------------------------------------------------------------
SQL Server MVP
http://visakhm.blogspot.com/
https://www.facebook.com/VmBlogs
Go to Top of Page

wahidullah
Starting Member

Afghanistan
5 Posts

Posted - 05/16/2013 :  06:36:16  Show Profile  Reply with Quote
if we dont create table for an entity, can we remove it from the ERD?

wahidullah290
Go to Top of Page

visakh16
Very Important crosS Applying yaK Herder

India
52317 Posts

Posted - 05/16/2013 :  06:42:39  Show Profile  Reply with Quote
hmm..Why is it that you dont need to create table if its already identified as an entity?
My point was inverse condition ie having more than one tables to represent same entity. I cant think of a case where you wont have a table for an already identified entity

------------------------------------------------------------------------------------------------------
SQL Server MVP
http://visakhm.blogspot.com/
https://www.facebook.com/VmBlogs
Go to Top of Page

wahidullah
Starting Member

Afghanistan
5 Posts

Posted - 05/19/2013 :  10:26:51  Show Profile  Reply with Quote
dear visakh:
I meant, is it necessary to create tables for each entity in the ERD?
if your answer is possitive then tell me the solution. I create ERD for a hospital and the reference relationship became the associative entity in this case I dont need to create table for reference. is it right?

wahidullah290
Go to Top of Page

visakh16
Very Important crosS Applying yaK Herder

India
52317 Posts

Posted - 05/20/2013 :  01:13:20  Show Profile  Reply with Quote
1. it is
2. reference relationship will ideally be represented by means of mapping table.

------------------------------------------------------------------------------------------------------
SQL Server MVP
http://visakhm.blogspot.com/
https://www.facebook.com/VmBlogs
Go to Top of Page
  Previous Topic Topic Next Topic  
 New Topic  Reply to Topic
 Printer Friendly
Jump To:
SQL Server Forums © 2000-2009 SQLTeam Publishing, LLC Go To Top Of Page
This page was generated in 0.06 seconds. Powered By: Snitz Forums 2000