Hi, >From my point of view, you should always add a autoincrement_field for having a unique identifier and keeping each record unique, ex. in case of programmingmistakes and so.
Best regards Peter ----- Original Message ----- From: "Mojtaba Faridzad" <[EMAIL PROTECTED]> To: <[EMAIL PROTECTED]> Sent: Thursday, June 19, 2003 5:15 PM Subject: selecting PRIMARY KEY when there is no unique value > Hi, > > In a docuement such as Invoice Form, we have a header and a couple of > records for the detail. In header table, Invoice# can be the PRIMARY KEY but > in detail table, Invoice# is not unique. I think there are two solutions to > choose a Primary Key (in MyISAM type) : > > 1) Adding an id field ( auto_increment ) and choose it as PRIMARY KEY > in this case we have to add another index on Invoice# for making relation > with the header table > > 2) There is another field in detail table with "timestamp" type for keeping > the last change on the record. I want to select ( Invoice# + myTimestamp ) > for PRIMARY KEY. in this case I don't need to add a new fields ( id ) and > another index ( on Invoice# ) to the table. > > which one do you prefer and usually use? > > thank > > > -- > MySQL General Mailing List > For list archives: http://lists.mysql.com/mysql > To unsubscribe: http://lists.mysql.com/[EMAIL PROTECTED] > > -- MySQL General Mailing List For list archives: http://lists.mysql.com/mysql To unsubscribe: http://lists.mysql.com/[EMAIL PROTECTED]
