Why can't a primary key be duplicated?

Why can't a primary key be duplicated in Access?

Because a primary key, by definition, identifies a unique record within a
table. If it can be duplicated, then you don't have uniquely identifiable
records in your table.
--

Ken Snell
http://www.accessmvp.com/KDSnell/


"torijoshmom" wrote in message
...
Why can't a primary key be duplicated in Access?

torijoshmom wrote:

Why can't a primary key be duplicated in Access?

For the same reason you can't have the same address referring to two
different buildings.

Tony
--
Tony Toews, Microsoft Access MVP
Tony's Main MS Access pages - http://www.granite.ab.ca/accsmstr.htm
Tony's Microsoft Access Blog - http://msmvps.com/blogs/access/
For a convenient utility to keep your users FEs and other files
updated see http://www.autofeupdater.com/
Granite Fleet Manager http://www.granitefleet.com/

It's not just Access. No relational database will allow duplicate data in the
primary key field of a table.
--
Jerry Whittle, Microsoft Access MVP
Light. Strong. Cheap. Pick two. Keith Bontrager - Bicycle Builder.


"torijoshmom" wrote:

Why can't a primary key be duplicated in Access?

Maybe if you describe the table, its definition, and the columns in the
table someone might be able to suggest a better data structure and/or a
better primary key. As others said, a unique primary key is a requirement in
a properly designed data structure.

"Jerry Whittle" wrote in message
...
It's not just Access. No relational database will allow duplicate data in
the
primary key field of a table.
--
Jerry Whittle, Microsoft Access MVP
Light. Strong. Cheap. Pick two. Keith Bontrager - Bicycle Builder.


"torijoshmom" wrote:

Why can't a primary key be duplicated in Access?

"torijoshmom" wrote in message
...
Why can't a primary key be duplicated in Access?

The reason for creating key constraints in a database is to help ensure the
integrity of the data. When you create any candidate key constraint you are
explicitly specifying a rule that says the DBMS must not allow data for the
key attributes to be duplicated. Any update that would cause duplication is
therefore rejected as an error.

If requirements change and you decide it's no longer appropriate to enforce
that rule then you should drop the candidate key constraint and define some
other key instead.

I recommend you study a book on database basics or take a good introductory
course because this is pretty fundamental stuff.

--
David Portas

thank you for shedding some light on the question. your input is greatly appreciated


---
frmsrcurl: http://msgroups.net/microsoft.public...-be-duplicated