Re: AutoNumber Question

again, i quite agree. even in cases where no natural key is available in a
table, Autonumber is not the only alternative, and certainly not the best
alternative in *every* situation.


"BruceM" <bamoob@xxxxxxxxxxxxxxxxxx> wrote in message
news:e4potKGaGHA.4424@xxxxxxxxxxxxxxxxxxxxxxx
Hi Tina,

I could have made it clearer that I was responding specifically to the
following:

"If it were a Database containing vehicle information, the VIN would not
be
a proper number to use a primary key identifier either (just like a SSN),
but instead a value relating to another value. And even then, a random
number, such as Access' AutoNumber should be used for the system to
identify
it and its uniqueness."

I just wanted to point out that there is no need to get stuck on using
such
a number. To say that something such as as autonumber *should* be used as
the PK is to create a rule where one is not needed.

"tina" <nospam@xxxxxxxxxxx> wrote in message
news:F%e3g.39457$az4.38385@xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx
you're quite right, Bruce - a primary key does not need to meaningless
to
the user. in this thread we were discussing specifically the
*Autonumber*
as
primary key, so the posted comments were applicable. i agree with you
also
that a unique value is not necessarily a good candidate for a natural
key
in
a table; that decision should be made on a table by table basis in every
relational data model, based on a number of factors that may or may not
be
unique to that business process.


"BruceM" <bamoob@xxxxxxxxxxxxxxxxxx> wrote in message
news:eGeGJA6ZGHA.3972@xxxxxxxxxxxxxxxxxxxxxxx
I would like to point out that a primary key does not need to be
meaningless
to the user. A sequential number such as 000001, 000002, etc. may be
used
for invoice numbers or the like. I don't see any reason why that
number
can't be the PK.
There are legal reasons why SSN should not be widely available in a
database, as it would be if it was part of relationships. However, I
would
think an employer would want to know if the number is not unique. If
John
Smith leaves the company, and five years later Jill Jones shows up with
John
Smith's SSN, I expect it would be a real mess for a company that simply
ignores the duplication.
A VIN as a PK could get a bit murky for an insurance company or the DMV
if
a
vehicle changes hands, but I expect either entity would want to know if
a
VIN is being reused. A VIN could make sense as a PK in some
situations.
Uniqueness is one thing; suitablility for use as a PK is another.
There
are
a lot of possible circumstances, each of which needs to be considered
separately.

"accessquestions" <vinootz@xxxxxxxxxxx> wrote in message
news:eSewKFzZGHA.3304@xxxxxxxxxxxxxxxxxxxxxxx
understood. I actually thought of that after I posted.
Just goes to show that it really takes an analytical mind to perfect
the
concepts of relational databases.
A VIN, like you state, serves a purpose, and is an attribute (an
important
one) of a vehicle. Not just a random number to identify it's
uniqueness
in a database. If it were a Database containing vehicle information,
the
VIN would not be a proper number to use a primary key identifier
either
(just like a SSN), but instead a value relating to another value.
And
even then, a random number, such as Aceess' AutoNumber should be used
for
the system to identify it and its uniqueness.
This dialogue was very educational for me as it relates to what I
have
read many times on the boards :put it all on paper first", and,
"determine
all information to be stored in the database and its relations to
other
tables" before creating them. If this was done, I would know that
the
SSN
and VIN Numbers were not suitable candidates for a Unique
Identifier.
Point Taken !
Thanks for all your insight ,as usual

VL


"tina" <nospam@xxxxxxxxxxx> wrote in message
news:DcS2g.35670$az4.17951@xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx
well, glad i could help. :)

but i have to point out that the VIN analogy is not apt. a VIN is
not
just a
collections of numbers/letters, it is a very specific code that
identifies
manufacturer, make and model of vehicle, model year of vehicle,
sometimes
where the vehicle was built, sometimes engine size, sometimes
maximum
payload for trucks, and other data - as well as the last 4 to 6
digits
that
are unique to a specific vehicle that is otherwise identical to many
other
vehicles in all those other respects. so a VIN has meaning separate
from
any
tracking database that stores it, and it must often be seen and used
directly by people - such as manufacturers, owners, insurers, DMVs.

an Autonumber primary key, on the other hand, has no meaning outside
of
the
database where the data is stored, and no meaning within the
database,
except to the software - and it absolutely should *not* be used with
the
idea of attaching a meaning to it. it also should not be seen by
anyone
who
uses the database, at any time - excepting only that the developer
may
look
at Autonumber values from time to time while building and/or
troubleshooting
the database.

hth


"accessquestions" <vinootz@xxxxxxxxxxx> wrote in message
news:exGDWOwZGHA.608@xxxxxxxxxxxxxxxxxxxxxxx
good point.
the Auto Number is sort like a VIN on a car, you rarely have to see
it,
but
its there and its serving a purpose,, and nobody committs it to
memory,
if
they would it would just confuse them. you convinced me, im an
auto
number
guy from now on.
thanks


"tina" <nospam@xxxxxxxxxxx> wrote in message
news:PAP2g.35270$az4.14873@xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx
well, personally, i would not use the SSN as a primary key, for 2
reasons.
first, SSNs are unfortunately not unique; there are many, many
duplicates
floating around out there. of course, only one person is using a
specific
SSN *legally*, but unless you want to get into tracking down
fraudulent
use... second, if you use the SSN as primary key, you'll have it
populating
multiple tables, potentially scattered all over your database.
again,
personally, i would safeguard an SSN the same way i would a
credit
card
number, in my database; put it in one place, and one place only,
so
it's
easier to protect by whatever means you use to secure proprietary
data.

having said all that, there's no reason you can't use an
Autonumber
as
the
primary key field for your employee table *as long as it is a
value
the
has
no meaning to anyone, only to Access*. your user should never see
an
Autonumber primary key, or use it directly to search for a record
in
the
table. don't confuse how your *user* finds a certain record in a
table
with
how *Access* identifies each record in a table. you can easily
use
an
Autonumber primary key and still allow your user to seach for an
employee
record using the person's SSN.

hth


"accessquestions" <vinootz@xxxxxxxxxxx> wrote in message
news:uhOmL0vZGHA.3652@xxxxxxxxxxxxxxxxxxxxxxx
Hello,
As far as a Primary Key is concerned (for an Employee Table)
I have read numerous times on the boards NOT to use the Auto
Number
feature,
I'm not sure exactly why, although I could see where the random
number
can
confuse some.
Would anyone recommend using a SSN instead? It will be unique,
and
it
will
serve as a good reference to the employee.
Any thoughts of why or why not?

Thanks Again !

VL


















.

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