| Creating PK in Each table [message #201715] |
Mon, 06 November 2006 08:28  |
selvakumar_82
Messages: 138
Registered: October 2005
Location: chennai
|
Senior Member |
|
|
Hi Friends,
If i create Primary Key in each table, it will be useful for future modification or maintainence.
because in one project i have seen primary key for all the tables.that project DB designer told me that
it will be more useful for future enhancements....
kindly i need answer from all experts
thanx and regards
Selva
|
|
|
|
| Re: Creating PK in Each table [message #201723 is a reply to message #201715] |
Mon, 06 November 2006 09:11  |
JRowbottom
Messages: 5933
Registered: June 2006
Location: Sunny North Yorkshire, ho...
|
Senior Member |
|
|
They're more than useful - if you don't have Primary and Foreign key constraints, you don't have a relational database - all you've got is a collection of data and a fond belief that it is in some way related.
Yes. You need Primary key constraints, and you also need Foreign key constraints.
|
|
|
|
|
|
| Re: Creating PK in Each table [message #202029 is a reply to message #201819] |
Tue, 07 November 2006 22:39 |
selvakumar_82
Messages: 138
Registered: October 2005
Location: chennai
|
Senior Member |
|
|
consider the following table:
User_id User_name password
In this case i can use USERNAME as a pk,
b coz username will be unique and not null.
So no need to create user_id right...?
In this kind of situation, what i have to do ....
or i have to keep Some ID as a PK in this table....?
Regards
Selva
|
|
|
|
| Re: Creating PK in Each table [message #202137 is a reply to message #202029] |
Wed, 08 November 2006 06:04 |
JRowbottom
Messages: 5933
Registered: June 2006
Location: Sunny North Yorkshire, ho...
|
Senior Member |
|
|
But, suppose user 'Amanda Smith' gets married and changes her name to 'Amanda Jones'?
If you have user_id column as the primary key, then you can just update the user_name and there are no problems.
If you are using user_name as the PK, then you need to either create a new user (in which case you need to record that these are the same person) or you need to update every place that has a FK link to this PK.
I'd use a user_id.
|
|
|
|
| Re: Creating PK in Each table [message #202142 is a reply to message #202137] |
Wed, 08 November 2006 06:31 |
selvakumar_82
Messages: 138
Registered: October 2005
Location: chennai
|
Senior Member |
|
|
ok,
Suppose in yahoo, we are not using user_id as a login.
more over we cant change user_name ,
If u want to change user_name u have to create another user_name only, we can change the password .
in this case what u will do.....? u will keep user_id as a PK or User_Name as a PK.....?
thanx and regards
Selva
|
|
|
|
|
|
| Re: Creating PK in Each table [message #202327 is a reply to message #202142] |
Thu, 09 November 2006 02:38 |
JRowbottom
Messages: 5933
Registered: June 2006
Location: Sunny North Yorkshire, ho...
|
Senior Member |
|
|
I'll have a User_id column as PK
Using fields that store information as primary keys is a generally bad idea.
"Users can't change their usernames" is just a business rule, and can be changed by the business.
My way - if it changes then there's no real problems.
Your way - if it changes then you've got an awful lot of work ahead of you.
Who is this 'u' bloke anyway?
|
|
|
|
] 
Blog
Search
Help
Members
Register
Login
Home
