Separate PK in Jxn Tbl?

Do you mean a bit like there are ISBN-10 and ISBN-13. Should I avoid using them and roll my own 'BookID'?

LOL! The US recently converted from the old UPC codes which were 10
digits to the 13 digit EAN system (ISBN13 was only a small part of
this) and will convert to the 15 digit GTIN in the near future.

Yet somehow we survived and nobody started printing their own bar code
labels again (yes, I am old enough to remember retail without UPC on
the packages).

The "immutable data" fallacy is that the identifier must get me to the
actual entity when I use it; it is free to mutate as it wishes as long
as it does its job. I have seen a security system in which the user
id is changing every five minutes or faster to prevent hacking. It
works great, but requires a memory stick in your PC to keep up with
things.

The advantage of standardized encodings is that I have a migration
path that is sponsored by an entire industry instead of having to do
everything myself.

I have yet to have any of them rise to the challenge of siting a single example of a correctly set up, split application in Access that isn't stable under load.

Home Depot's contractor tracking system on ACCESS? It's failures are
famous in Atlanta.

David Cressey wrote:

database, is qualitatively different from the design target of the people
who write Access databases and applications.

If they ever get to the point where the complexity of what they are doing
matches the complexity of what practitioners using SQL Server, Oracle, or
DB2 are doing, or the complexity that database theorists are addressing,
they will be forced to either learn or disprove what some of us know, or
think we know.

I don't have broad enough experience to dispute your argument. I
understand that people who specialize in SQL and deal with more complex
situations than most develop practices that make use of their more
intimate knowledge of SQL. However, I can't just take their word about
their decisions. I have to understand how those choices apply to what
I'm doing. Without making light of their potential contribution, I
avoid the specious argument that because a large company or IT
department does things a certain way or spends more money on the problem
makes their solution inherently correct. Plus, the complexity of the
problems they face often argue against their use in Access. Few Access
developers have the luxury to hire or supervise a full-time SQL
developer. If using multiple field natural keys causes a problem(s), a
full-time SQL developer has time to work with the SQL until the problem
is solved. SQL is only part of our job.

It has been nice to see posters in microsoft.public.access such as Jamie
Collins and Ken Sheridan, who seem to have a lot of standard SQL
experience, branch off into other issues that Access programmers face.
I think their understanding of those issues can help us differentiate
between purely SQL issues and Microsoft implementation issues. We all
agree that Microsoft has made questionable design decisions in Access,
but the possibility of inclusion of unbound forms or of AutoNumber
primary keys might not be part of that list, as some have suggested. I
have enough experience to say that using unbound forms in Access and
using artificial keys did not cause any problems when scaling an Access
application up to an ASP solution using SQL Server. For something more
complicated perhaps there are subtle issues that arise that merit our
attention.

Table level constraints also raise an issue. At the table level, there
is no VBA code run to ensure that any constraints (e.g., on the natural
keys themselves) are enforced. Thus, a set of natural keys is
sufficient to specify the key constraint. Any artificial key becomes
superfluous. The possibility of separate applications using the same
table, brought up by David Fenton, brings up the interesting possibility
that the applications have separate, possibly disparate constraints. In
disparate constraint situations not all of the constraints can be at the
table level, although they can be specified at the query level in each
application rather than via code.

Maybe many Access programmers prefer a single key to limit the number of
fields that get corrupted :-). Perhaps an enumeration of sticky
situations encountered by those using multiple field natural keys would
help us understand why some avoid them. Maybe better solutions to those
sticky problems would encourage developers to stay with natural keys
more often.

James A. Fortune

-CELKO- wrote:
I have yet to have any of them rise to the challenge of siting a
single example of a correctly set up, split application in Access
that isn't stable under load.


Home Depot's contractor tracking system on ACCESS? It's failures are
famous in Atlanta.

You object of derision is the application whereas an outsider like me
would assume management, specs, and skill level created the failure.
AFAIC, the programmers in CDMA are world class folks and obviously were
not part of the project you brought up.

Dilbert management providing ill thought out/band-aid specs while
employing low-level programmers that don't speak English can create a
famous failure. By chance are you on the failure's committee?

Do you have any links to the famous failure you mentioned? It might
make for a fun read of management incompetency.

If you do respond, be sure to cut out all my post so nobody knows who
you are responding to and make it appear you are talking to yourself for
no particular reason.

It is a good classic screw up, with blame for everyone!

1) ACCESS programmer builds desktop app on his own that looks good for
his immediate needs.
2) Management sees the app and wants to deploy it all over the
company. Hey, why design anything new when we have it already?
3) ACCESS programmer claims it will deploy and and management believes
him.
4) It does not scale, it does not interface with mainframe apps,
external apps, etc. It has no documentation, etc.
5) ACCESS programmer now has a career being the only guy who can keep
the sinking boat up. Never mind how many times a week it has to be re-
booted or how much data is lost.
6) Neither the programmer nor management will scream for help and ask
for a budget. Management would look stupid; programmer would lose his
job and power

"James A. Fortune" wrote in message
...
David Cressey wrote:

database, is qualitatively different from the design target of the people
who write Access databases and applications.

If they ever get to the point where the complexity of what they are doing
matches the complexity of what practitioners using SQL Server, Oracle, or
DB2 are doing, or the complexity that database theorists are addressing,
they will be forced to either learn or disprove what some of us know, or
think we know.

I don't have broad enough experience to dispute your argument. I
understand that people who specialize in SQL and deal with more complex
situations than most develop practices that make use of their more
intimate knowledge of SQL. However, I can't just take their word about
their decisions. I have to understand how those choices apply to what I'm
doing. Without making light of their potential contribution, I avoid the
specious argument that because a large company or IT department does
things a certain way or spends more money on the problem makes their
solution inherently correct. Plus, the complexity of the problems they
face often argue against their use in Access. Few Access developers have
the luxury to hire or supervise a full-time SQL developer. If using
multiple field natural keys causes a problem(s), a full-time SQL developer
has time to work with the SQL until the problem is solved. SQL is only
part of our job.

It has been nice to see posters in microsoft.public.access such as Jamie
Collins and Ken Sheridan, who seem to have a lot of standard SQL
experience, branch off into other issues that Access programmers face. I
think their understanding of those issues can help us differentiate
between purely SQL issues and Microsoft implementation issues. We all
agree that Microsoft has made questionable design decisions in Access, but
the possibility of inclusion of unbound forms or of AutoNumber primary
keys might not be part of that list, as some have suggested. I have
enough experience to say that using unbound forms in Access and using
artificial keys did not cause any problems when scaling an Access
application up to an ASP solution using SQL Server. For something more
complicated perhaps there are subtle issues that arise that merit our
attention.

Table level constraints also raise an issue. At the table level, there is
no VBA code run to ensure that any constraints (e.g., on the natural keys
themselves) are enforced. Thus, a set of natural keys is sufficient to
specify the key constraint. Any artificial key becomes superfluous. The
possibility of separate applications using the same table, brought up by
David Fenton, brings up the interesting possibility that the applications
have separate, possibly disparate constraints. In disparate constraint
situations not all of the constraints can be at the table level, although
they can be specified at the query level in each application rather than
via code.


Constraints should always be checked by the DBMS, not by applications. If
you have two separate applications that manipulate the same table, and one
enforces one constraint while another enforces another, then all you need to
do to bypass one constraint is to use the other application! What, then, is
the point of even having the constraint?

Maybe many Access programmers prefer a single key to limit the number of
fields that get corrupted :-). Perhaps an enumeration of sticky
situations encountered by those using multiple field natural keys would
help us understand why some avoid them. Maybe better solutions to those
sticky problems would encourage developers to stay with natural keys more
often.


In my opinion, the only sound reason for using artificial keys is when the
values of a natural key do not permanently identify individuals in the
Universe of Discourse--that is, the micro-world that the database is
supposed to be a model of--and when there is a demonstrable requirement for
permanent identification. Any other use adds complexity for complexities
sake--in other words, for no particularly good reason.

James A. Fortune

In my opinion, the only sound reason for using artificial keys is when the
values of a natural key do not permanently identify individuals in the
Universe of Discourse--that is, the micro-world that the database is
supposed to be a model of--and when there is a demonstrable requirement
for permanent identification. Any other use adds complexity for
complexities sake--in other words, for no particularly good reason.

Even in the very few cases were you think that a natural key will be a true
natural key, ie. it will be permanent and totally managed at 100% (which
mean no data entry error of any kind, no change of value because of identity
theft, etc., etc.); the privacy issues will forbid their use in many cases.
Many countries now forbid by law to ask for something such as your social
security number when you don't need it and when you need it, to use it as a
key instead of storing it confidentially (ie., by encrypting it).

Even MS had problem with this in the past: the first version of the
algorithm for generating a GUIG was using the NIC number as part of its
algorithm. They had to remove it later and now, the generation of any GUIG
is totally random. The older algorithm is still available in Windows under
another name but MS warns that anyone using it might be doing so illegally
under the laws of their countries.

The same argument apply to things like RFID: how many of you would like to
see big corporation to know which medicaments you are bringing home or your
spouse to know that you have just bought a box of condom?

Using natural keys is like building a castle of cards: they might look
impressive but it doesn't take to much to bring them down.

--
Sylvain Lafontaine, ing.
MVP - Technologies Virtual-PC
E-mail: sylvain aei ca (fill the blanks, no spam please)


"Brian Selzer" wrote in message
news

"James A. Fortune" wrote in message
...
David Cressey wrote:

database, is qualitatively different from the design target of the
people
who write Access databases and applications.

If they ever get to the point where the complexity of what they are
doing
matches the complexity of what practitioners using SQL Server, Oracle,
or
DB2 are doing, or the complexity that database theorists are
addressing,
they will be forced to either learn or disprove what some of us know, or
think we know.

I don't have broad enough experience to dispute your argument. I
understand that people who specialize in SQL and deal with more complex
situations than most develop practices that make use of their more
intimate knowledge of SQL. However, I can't just take their word about
their decisions. I have to understand how those choices apply to what
I'm doing. Without making light of their potential contribution, I avoid
the specious argument that because a large company or IT department does
things a certain way or spends more money on the problem makes their
solution inherently correct. Plus, the complexity of the problems they
face often argue against their use in Access. Few Access developers have
the luxury to hire or supervise a full-time SQL developer. If using
multiple field natural keys causes a problem(s), a full-time SQL
developer has time to work with the SQL until the problem is solved. SQL
is only part of our job.

It has been nice to see posters in microsoft.public.access such as Jamie
Collins and Ken Sheridan, who seem to have a lot of standard SQL
experience, branch off into other issues that Access programmers face. I
think their understanding of those issues can help us differentiate
between purely SQL issues and Microsoft implementation issues. We all
agree that Microsoft has made questionable design decisions in Access,
but the possibility of inclusion of unbound forms or of AutoNumber
primary keys might not be part of that list, as some have suggested. I
have enough experience to say that using unbound forms in Access and
using artificial keys did not cause any problems when scaling an Access
application up to an ASP solution using SQL Server. For something more
complicated perhaps there are subtle issues that arise that merit our
attention.

Table level constraints also raise an issue. At the table level, there
is no VBA code run to ensure that any constraints (e.g., on the natural
keys themselves) are enforced. Thus, a set of natural keys is sufficient
to specify the key constraint. Any artificial key becomes superfluous.
The possibility of separate applications using the same table, brought up
by David Fenton, brings up the interesting possibility that the
applications have separate, possibly disparate constraints. In disparate
constraint situations not all of the constraints can be at the table
level, although they can be specified at the query level in each
application rather than via code.


Constraints should always be checked by the DBMS, not by applications. If
you have two separate applications that manipulate the same table, and one
enforces one constraint while another enforces another, then all you need
to do to bypass one constraint is to use the other application! What,
then, is the point of even having the constraint?

Maybe many Access programmers prefer a single key to limit the number of
fields that get corrupted :-). Perhaps an enumeration of sticky
situations encountered by those using multiple field natural keys would
help us understand why some avoid them. Maybe better solutions to those
sticky problems would encourage developers to stay with natural keys more
often.


In my opinion, the only sound reason for using artificial keys is when the
values of a natural key do not permanently identify individuals in the
Universe of Discourse--that is, the micro-world that the database is
supposed to be a model of--and when there is a demonstrable requirement
for permanent identification. Any other use adds complexity for
complexities sake--in other words, for no particularly good reason.

James A. Fortune

-CELKO- wrote:

It is a good classic screw up, with blame for everyone!

1) ACCESS programmer builds desktop app on his own that looks good for
his immediate needs.
2) Management sees the app and wants to deploy it all over the
company. Hey, why design anything new when we have it already?
3) ACCESS programmer claims it will deploy and and management believes
him.
4) It does not scale, it does not interface with mainframe apps,
external apps, etc. It has no documentation, etc.
5) ACCESS programmer now has a career being the only guy who can keep
the sinking boat up. Never mind how many times a week it has to be re-
booted or how much data is lost.
6) Neither the programmer nor management will scream for help and ask
for a budget. Management would look stupid; programmer would lose his
job and power

That sounds quite typical for some Access applications. But consider just where was
IT in all this? D*cking around on their Oracle database that will save the company.
Or this app didn't fit in the IT priorities. We'll create this fabulous system.
Uhh, when? Sometime this century.

It's better than Excel. Although not by much in such incapable hands as you
describe. And that I've seen myself in the past.

Tony
--
Tony Toews, Microsoft Access MVP
Please respond only in the newsgroups so that others can
read the entire thread of messages.
Microsoft Access Links, Hints, Tips & Accounting Systems at
http://www.granite.ab.ca/accsmstr.htm
Tony's Microsoft Access Blog - http://msmvps.com/blogs/access/

"Brian Selzer" wrote in message
news

Constraints should always be checked by the DBMS, not by applications.

I agree very heartily with the first part of this statement, for the reasons
you give below. I disagree with the second part (as stated). There is no
reason why applications shouldn't also test what constraints they can. The
problem is that they should not have hand-coded re-implementations of the
constraints because those will get out of sync with the database over time.
What would be very nice is if one day it were possible for applications to
download the relevant constraints at run-time, the way they presently
download other metda-data.

If you have two separate applications that manipulate the same table, and
one enforces one constraint while another enforces another, then all you
need to do to bypass one constraint is to use the other application!
What, then, is the point of even having the constraint?

Roy

"James A. Fortune" wrote in message
...
Sylvain Lafontaine wrote:
I concede the point that for the two keys of the junction table, using
an
autonumber primary key is overkill except for special situations.


Shouldn't a database be designed right from the beginning?


I didn't say overkill doesn't work, did I :-)? I think that until we
delineate the true trade-offs between natural keys and artificial keys,
if any, you should design your schemas/schemata as you deem best. If it
turns out that there are situations where each has advantages then those
situations should determine the correctness of the schema.

I'll go further than that. For most design problems there is more than one
acceptable solution. This is particularly true of schema design. Design
trade-offs will help determine which of two possible designs is better in
any given situation.