Re: Beginner help needed in database design

On Tue, 1 Feb 2005 12:53:25 -0700, "Mark A" <nobody_at_nowhere.com> wrote:

>"Drago Ganic" <drago.ganic_at_in2.hr> wrote in message
>news:ctom21$ak5$1_at_ls219.htnet.hr...
>> Frank,
>> that is simply wrong. Primary key is a integrity constraint! Constraints
>are
>> logic statements. This has nothing to do with technology. Your and my
>> >>Surname + Name<< are intended to be primary keys for us - bad ones as
>we
>> know. Threrfore we have SSN etc.
>>
>> Keys are needed for >>identification<< of the other data -- which are for
>> >>description<<.
>>
>> Databases (the relational ones for sure) are data + constraints, not just
>> data! Historically the most used constraints just happen to be primary
>(and
>> foreign) keys because of the identification problem.
>>
>> Greetings from Croatia,
>> Drago
>>
>Primary keys and foreign keys are a DBMS enforced referential constraints.
>Prior to about 1988, primary and foreign keys did not exist, even in
>relational databases (at least not in database that I recall).
>

Oh???? As early as 1985 I was doing applications programming in COBOL against IMS (a hierarchical database by IBM) and they had primary keys. Between 1981 and 1985 it was VSAM KSDS files, also with primary keys. Now, that's been a few years. Maybe they weren't *called* "primary key", but that's what they were -- a value that was unique to a particular record in the data store.

>Referential integrity can also be enforced by application programs that
>insert, update, or delete data, as it had to be done (if needed) before
>primary and foreign keys were made part of databases.
>

Thanks.

• Ed Stevens

Cohn's Law: The more time you spend in reporting on what you are doing, the less time you have to do anything. Stability is achieved when you spend all your time doing nothing but reporting on the nothing you are doing. Received on Wed Feb 02 2005 - 07:43:15 CST