Dear all,

Although many Microsoft Access books advise to set an autonumber field as
primary index (a so called pseudo primary key),
http://www.blueclaw-db.com/database_link_tables.htm advises to use real data
to define a (composite) primary key. In summary, this results in the
following two designs:

>Microsoft Acces books setup for Employee table
Employee_ID (autonumber, primary key)
SSN (social security number, composite index key1)
Employee_Name (full employee name, composite index key2)
composite index SSN + Employee_Name = unique

>BlueClaw setup for Employee table
Employee_ID (autonumber, unique index)
SSN (social security number, (composite) primary key1)
Employee_Name (full employee name, (composite) primary key2)

In both approaches, Employee_ID would be used as a foreign key in other
tables to define the relationship with the Employee table.

Are there any negative aspects associated with the BlueClaw approach?

Pros of BlueClaw approach
*Display of table is meaningful, because it's sorted on primary index
*No cascaded update necessary of linked relationship fields in other tables,
because autonumber is only used for linking tables and therefore will never
change.
*Prevention of duplicates is improved, since data fields are used to check
for duplicates, instead of an (always unique) autonumber field > this can
also be achieved with the composite unique index as shown above in the Access
books example.

Cons of BlueClaw approach
*???

I would appreciate your comments / opinion on the BlueClaw approach, because
I currently have the feeling that I'm missing something that explains why so
many people use autonumber fields as primary (artificial) key. If the
BlueClaw approach is the best one, I'm considering to use it as a standard in
new database design questions.

Best regards,

M.

You may have just inflamed a long-running religious war about proper primary
keys.<g>

See comments in-line below...

"M." <(E-Mail Removed)> wrote in message
news:5C60984F-9FD8-4E90-93FF-(E-Mail Removed)...
> Dear all,
>
> Although many Microsoft Access books advise to set an autonumber field as
> primary index (a so called pseudo primary key),

"psuedo" implies "not real" -- a primary key is a unique identifier, no
matter where it comes from. It isn't a question of "real".

> http://www.blueclaw-db.com/database_link_tables.htm advises to use real
> data
> to define a (composite) primary key. In summary, this results in the
> following two designs:
>
>>Microsoft Acces books setup for Employee table
> Employee_ID (autonumber, primary key)
> SSN (social security number, composite index key1)

you will want to be very careful about capturing/displaying SSNs. Moreover,
not every "person" has (or cares to share) one. How will you handle a Null
SSN?

> Employee_Name (full employee name, composite index key2)

No, no no! If you combine more than one fact in a single field, you have to
work extra hard to do simple things, like, say, sort by LAST NAME! Use
FirstName and LastName fields, then use a query to concatenate them when
needed.

> composite index SSN + Employee_Name = unique

can you say "identity theft"? what makes you think that SSN + Employee_Name
will be unique?

>
>>BlueClaw setup for Employee table
> Employee_ID (autonumber, unique index)

Why? By definition, an Autonumber is supposed to already be unique, so you
wouldn't gain anything by indexing it.

> SSN (social security number, (composite) primary key1)

(see above)

> Employee_Name (full employee name, (composite) primary key2)

(see above)

>
> In both approaches, Employee_ID would be used as a foreign key in other
> tables to define the relationship with the Employee table.

If you go to the effort of creating a composite primary key, then why would
you not also go to the effort to "migrate" that key (i.e., all fields) to
the "child" tables?

>
> Are there any negative aspects associated with the BlueClaw approach?
>
> Pros of BlueClaw approach
> *Display of table is meaningful, because it's sorted on primary index

No, NO, NO!! Access tables store data, Access forms (and reports) display
it. Using Access tables to display data is asking for trouble! (can you
tell I have some strong feelings on this topic?<g> - check this newsgroup
for others' ideas about using tables to display data. From experience, I
don't want inexperienced users mucking about directly in my tables.
Instead, I'll guide their use of the data via forms. This is a major
difference between, say, Word {everyone knows how to move words around} and
Access, a relational database {how many normal people understand relational
database design?})

And "meaningful"?! To whom? Just because a set of data is sorted in one
order doesn't mean that EVERYONE wants to see it in that order. I, for one,
prefer to see a list of employees sorted by last name when I'm considering
Human Resources activities, but by firstname when I'm looking for their
phone numbers.

> *No cascaded update necessary of linked relationship fields in other
> tables,
> because autonumber is only used for linking tables and therefore will
> never
> change.

The implication is that the SSN and Employee_Name MAY change. So what?
There's next to zero effort required to set Cascading Updates when you set
the relationships among tables. And while an Autonumber may not change, you
can re-record a row of data and get a NEW autonumber, then delete the old
record. Where's your foreign key now?!

> *Prevention of duplicates is improved, since data fields are used to check
> for duplicates, instead of an (always unique) autonumber field > this can
> also be achieved with the composite unique index as shown above in the
> Access
> books example.

Ahem! ?"Duplicates"? Are the following employees the same person:
John Doe
J. J. Doe
And what about John and his son John, who both work for your company, both
live at the same address, and both have the same last name. ?Duplicates?!

>
> Cons of BlueClaw approach
> *???
>
> I would appreciate your comments / opinion on the BlueClaw approach,
> because
> I currently have the feeling that I'm missing something that explains why
> so
> many people use autonumber fields as primary (artificial) key. If the
> BlueClaw approach is the best one, I'm considering to use it as a standard
> in
> new database design questions.

JOPO (just one person's opinion) Any approach to this that claims to be the
one and only appropriate way to do this is probably wrong! Use what works
for you.

Regards

Jeff Boyce
Microsoft Office/Access MVP

>
> Best regards,
>
> M.

Thanks for your reply, but unfortunately this doesn't answer my question. I'm
sorry to distract you with minor issues, like the SSN and name fields. These
were copied from the Blue Claw example on their website. Of course I'm aware
of full name issues, but that's not my question.

My main question is: are there negative aspects associated with using a
primary key based on data fields versus using a primary key based on an
artificial primary key as generated with an autonumber field? In both cases
the autonumber field would be used for defining relations between tables.

Until now my answer would be: there are no negative aspects associated with
the data fields approach.

Best regards,

M.


"Jeff Boyce" wrote:

> You may have just inflamed a long-running religious war about proper primary
> keys.<g>
>
> See comments in-line below...
>
> "M." <(E-Mail Removed)> wrote in message
> news:5C60984F-9FD8-4E90-93FF-(E-Mail Removed)...
> > Dear all,
> >
> > Although many Microsoft Access books advise to set an autonumber field as
> > primary index (a so called pseudo primary key),
>
> "psuedo" implies "not real" -- a primary key is a unique identifier, no
> matter where it comes from. It isn't a question of "real".
>
> > http://www.blueclaw-db.com/database_link_tables.htm advises to use real
> > data
> > to define a (composite) primary key. In summary, this results in the
> > following two designs:
> >
> >>Microsoft Acces books setup for Employee table
> > Employee_ID (autonumber, primary key)
> > SSN (social security number, composite index key1)
>
> you will want to be very careful about capturing/displaying SSNs. Moreover,
> not every "person" has (or cares to share) one. How will you handle a Null
> SSN?
>
> > Employee_Name (full employee name, composite index key2)
>
> No, no no! If you combine more than one fact in a single field, you have to
> work extra hard to do simple things, like, say, sort by LAST NAME! Use
> FirstName and LastName fields, then use a query to concatenate them when
> needed.
>
> > composite index SSN + Employee_Name = unique
>
> can you say "identity theft"? what makes you think that SSN + Employee_Name
> will be unique?
>
> >
> >>BlueClaw setup for Employee table
> > Employee_ID (autonumber, unique index)
>
> Why? By definition, an Autonumber is supposed to already be unique, so you
> wouldn't gain anything by indexing it.
>
> > SSN (social security number, (composite) primary key1)
>
> (see above)
>
> > Employee_Name (full employee name, (composite) primary key2)
>
> (see above)
>
> >
> > In both approaches, Employee_ID would be used as a foreign key in other
> > tables to define the relationship with the Employee table.
>
> If you go to the effort of creating a composite primary key, then why would
> you not also go to the effort to "migrate" that key (i.e., all fields) to
> the "child" tables?
>
> >
> > Are there any negative aspects associated with the BlueClaw approach?
> >
> > Pros of BlueClaw approach
> > *Display of table is meaningful, because it's sorted on primary index
>
> No, NO, NO!! Access tables store data, Access forms (and reports) display
> it. Using Access tables to display data is asking for trouble! (can you
> tell I have some strong feelings on this topic?<g> - check this newsgroup
> for others' ideas about using tables to display data. From experience, I
> don't want inexperienced users mucking about directly in my tables.
> Instead, I'll guide their use of the data via forms. This is a major
> difference between, say, Word {everyone knows how to move words around} and
> Access, a relational database {how many normal people understand relational
> database design?})
>
> And "meaningful"?! To whom? Just because a set of data is sorted in one
> order doesn't mean that EVERYONE wants to see it in that order. I, for one,
> prefer to see a list of employees sorted by last name when I'm considering
> Human Resources activities, but by firstname when I'm looking for their
> phone numbers.
>
> > *No cascaded update necessary of linked relationship fields in other
> > tables,
> > because autonumber is only used for linking tables and therefore will
> > never
> > change.
>
> The implication is that the SSN and Employee_Name MAY change. So what?
> There's next to zero effort required to set Cascading Updates when you set
> the relationships among tables. And while an Autonumber may not change, you
> can re-record a row of data and get a NEW autonumber, then delete the old
> record. Where's your foreign key now?!
>
> > *Prevention of duplicates is improved, since data fields are used to check
> > for duplicates, instead of an (always unique) autonumber field > this can
> > also be achieved with the composite unique index as shown above in the
> > Access
> > books example.
>
> Ahem! ?"Duplicates"? Are the following employees the same person:
> John Doe
> J. J. Doe
> And what about John and his son John, who both work for your company, both
> live at the same address, and both have the same last name. ?Duplicates?!
>
> >
> > Cons of BlueClaw approach
> > *???
> >
> > I would appreciate your comments / opinion on the BlueClaw approach,
> > because
> > I currently have the feeling that I'm missing something that explains why
> > so
> > many people use autonumber fields as primary (artificial) key. If the
> > BlueClaw approach is the best one, I'm considering to use it as a standard
> > in
> > new database design questions.
>
> JOPO (just one person's opinion) Any approach to this that claims to be the
> one and only appropriate way to do this is probably wrong! Use what works
> for you.
>
> Regards
>
> Jeff Boyce
> Microsoft Office/Access MVP
>
> >
> > Best regards,
> >
> > M.
>
>
>

ANY data can be used as a Primary Key AS LONG AS you are 100% sure of no
duplication and/or have code in place to prevent such an occurrance. I've
been a database designer for over 30 years, and until I started working with
MS Access, there was NO SUCH THING as an "autonumber key." EVERY key/primary
key was based on data. And several of my projects written in Access use
data-based keys/primaries.



"M." wrote:

> Thanks for your reply, but unfortunately this doesn't answer my question. I'm
> sorry to distract you with minor issues, like the SSN and name fields. These
> were copied from the Blue Claw example on their website. Of course I'm aware
> of full name issues, but that's not my question.
>
> My main question is: are there negative aspects associated with using a
> primary key based on data fields versus using a primary key based on an
> artificial primary key as generated with an autonumber field? In both cases
> the autonumber field would be used for defining relations between tables.
>
> Until now my answer would be: there are no negative aspects associated with
> the data fields approach.
>
> Best regards,
>
> M.
>
>
> "Jeff Boyce" wrote:
>
> > You may have just inflamed a long-running religious war about proper primary
> > keys.<g>
> >
> > See comments in-line below...
> >
> > "M." <(E-Mail Removed)> wrote in message
> > news:5C60984F-9FD8-4E90-93FF-(E-Mail Removed)...
> > > Dear all,
> > >
> > > Although many Microsoft Access books advise to set an autonumber field as
> > > primary index (a so called pseudo primary key),
> >
> > "psuedo" implies "not real" -- a primary key is a unique identifier, no
> > matter where it comes from. It isn't a question of "real".
> >
> > > http://www.blueclaw-db.com/database_link_tables.htm advises to use real
> > > data
> > > to define a (composite) primary key. In summary, this results in the
> > > following two designs:
> > >
> > >>Microsoft Acces books setup for Employee table
> > > Employee_ID (autonumber, primary key)
> > > SSN (social security number, composite index key1)
> >
> > you will want to be very careful about capturing/displaying SSNs. Moreover,
> > not every "person" has (or cares to share) one. How will you handle a Null
> > SSN?
> >
> > > Employee_Name (full employee name, composite index key2)
> >
> > No, no no! If you combine more than one fact in a single field, you have to
> > work extra hard to do simple things, like, say, sort by LAST NAME! Use
> > FirstName and LastName fields, then use a query to concatenate them when
> > needed.
> >
> > > composite index SSN + Employee_Name = unique
> >
> > can you say "identity theft"? what makes you think that SSN + Employee_Name
> > will be unique?
> >
> > >
> > >>BlueClaw setup for Employee table
> > > Employee_ID (autonumber, unique index)
> >
> > Why? By definition, an Autonumber is supposed to already be unique, so you
> > wouldn't gain anything by indexing it.
> >
> > > SSN (social security number, (composite) primary key1)
> >
> > (see above)
> >
> > > Employee_Name (full employee name, (composite) primary key2)
> >
> > (see above)
> >
> > >
> > > In both approaches, Employee_ID would be used as a foreign key in other
> > > tables to define the relationship with the Employee table.
> >
> > If you go to the effort of creating a composite primary key, then why would
> > you not also go to the effort to "migrate" that key (i.e., all fields) to
> > the "child" tables?
> >
> > >
> > > Are there any negative aspects associated with the BlueClaw approach?
> > >
> > > Pros of BlueClaw approach
> > > *Display of table is meaningful, because it's sorted on primary index
> >
> > No, NO, NO!! Access tables store data, Access forms (and reports) display
> > it. Using Access tables to display data is asking for trouble! (can you
> > tell I have some strong feelings on this topic?<g> - check this newsgroup
> > for others' ideas about using tables to display data. From experience, I
> > don't want inexperienced users mucking about directly in my tables.
> > Instead, I'll guide their use of the data via forms. This is a major
> > difference between, say, Word {everyone knows how to move words around} and
> > Access, a relational database {how many normal people understand relational
> > database design?})
> >
> > And "meaningful"?! To whom? Just because a set of data is sorted in one
> > order doesn't mean that EVERYONE wants to see it in that order. I, for one,
> > prefer to see a list of employees sorted by last name when I'm considering
> > Human Resources activities, but by firstname when I'm looking for their
> > phone numbers.
> >
> > > *No cascaded update necessary of linked relationship fields in other
> > > tables,
> > > because autonumber is only used for linking tables and therefore will
> > > never
> > > change.
> >
> > The implication is that the SSN and Employee_Name MAY change. So what?
> > There's next to zero effort required to set Cascading Updates when you set
> > the relationships among tables. And while an Autonumber may not change, you
> > can re-record a row of data and get a NEW autonumber, then delete the old
> > record. Where's your foreign key now?!
> >
> > > *Prevention of duplicates is improved, since data fields are used to check
> > > for duplicates, instead of an (always unique) autonumber field > this can
> > > also be achieved with the composite unique index as shown above in the
> > > Access
> > > books example.
> >
> > Ahem! ?"Duplicates"? Are the following employees the same person:
> > John Doe
> > J. J. Doe
> > And what about John and his son John, who both work for your company, both
> > live at the same address, and both have the same last name. ?Duplicates?!
> >
> > >
> > > Cons of BlueClaw approach
> > > *???
> > >
> > > I would appreciate your comments / opinion on the BlueClaw approach,
> > > because
> > > I currently have the feeling that I'm missing something that explains why
> > > so
> > > many people use autonumber fields as primary (artificial) key. If the
> > > BlueClaw approach is the best one, I'm considering to use it as a standard
> > > in
> > > new database design questions.
> >
> > JOPO (just one person's opinion) Any approach to this that claims to be the
> > one and only appropriate way to do this is probably wrong! Use what works
> > for you.
> >
> > Regards
> >
> > Jeff Boyce
> > Microsoft Office/Access MVP
> >
> > >
> > > Best regards,
> > >
> > > M.
> >
> >
> >

"M." <(E-Mail Removed)> wrote in message
news:124E0144-170B-4DC5-A4F9-(E-Mail Removed)...
>
> My main question is: are there negative aspects associated with using a
> primary key based on data fields versus using a primary key based on an
> artificial primary key as generated with an autonumber field? In both
> cases
> the autonumber field would be used for defining relations between tables.

There's no reason to have an Autonumber field AND a "natural" primary key.

If you're going to create relationships, they will always be based on the
primary key. You cannot change that.

As Jeff said, this really is a religious war, so I won't say any more. <g>

--
Doug Steele, Microsoft Access MVP
http://I.Am/DougSteele
(no private e-mails, please)

A primary key is a SINGLE field used as the record identifier. It really
should have no meaning to the user and in most cases never seam by users.

In all the databases that have worked with the have multiple fields for a
primary key have made it a lot harder to do anything, even things that should
be simple. I would never create one that way. I probably am glad the there
are people that recommend it (like Blue Claw) or actually do it so that I
will get lots of work fixing the issues it causes.

--
Boyd Trimmell
aka HiTechCoach
http://www.hitechcoach.com
http://www.officeprogramming.com

Message posted via AccessMonster.com
http://www.accessmonster.com/Uwe/For...esign/200712/1

On Tue, 4 Dec 2007 17:53:43 -0500, "Douglas J. Steele"
<NOSPAM_djsteele@NOSPAM_canada.com> wrote:

>"M." <(E-Mail Removed)> wrote in message
>news:124E0144-170B-4DC5-A4F9-(E-Mail Removed)...
>>
>> My main question is: are there negative aspects associated with using a
>> primary key based on data fields versus using a primary key based on an
>> artificial primary key as generated with an autonumber field? In both
>> cases
>> the autonumber field would be used for defining relations between tables.
>
>There's no reason to have an Autonumber field AND a "natural" primary key.
>
>If you're going to create relationships, they will always be based on the
>primary key. You cannot change that.
>
>As Jeff said, this really is a religious war, so I won't say any more. <g>

This works for me. It seems to go against what you are saying.

Sub CreateTest()
With CurrentProject.Connection

..Execute _
"CREATE TABLE Cities" & _
" (city_id IDENTITY (1,1) NOT NULL UNIQUE" & _
",city_name VARCHAR (30) NOT NULL" & _
",PRIMARY KEY (city_name));"

..Execute _
"CREATE TABLE States" & _
" (state_id IDENTITY(1,1) NOT NULL UNIQUE" & _
",state_name VARCHAR (30) NOT NULL" & _
",PRIMARY KEY (state_name));"

..Execute _
" CREATE TABLE Locations" & _
" (location_id IDENTITY (1,1) NOT NULL UNIQUE" & _
",city_id INTEGER NOT NULL" & _
" REFERENCES Cities (city_id)" & _
",state_id INTEGER NOT NULL" & _
" REFERENCES States (state_id)" & _
",PRIMARY KEY (city_id, state_id));"

End With
End Sub

M. <(E-Mail Removed)> wrote:

>>BlueClaw setup for Employee table

BlueClaw are full of cr*p. The middle sentence in the following is
exceedingly arrogant.

"You may look at this design and say you have always seen the
Employee_ID set as the table primary key. No matter what your teacher
or books say - this would be incorrect. See why you almost never use
an artificially generated numeric ID as a primary key."

As far as thier "Table Design Example - Detail Table" goes it's based
on a very faulty assumption. That the employee only does one task
throughout the day. And that's seldom the case.

And they don't explain themselves very well either.

As Jeff states this can become a religious war.

In my opinion use autonumber primary keys on every table and unique
and duplicate indexes as appropriate.

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/

A primary key does NOT have to be a single field.

A primary key is simply a special unique index, and therefore can contain up
to ten separate fields.

Perhaps you're thinking of an Autonumber field when you say "It really
should have no meaning to the user and in most cases never seam by users."


--
Doug Steele, Microsoft Access MVP
http://I.Am/DougSteele
(no private e-mails, please)


"Boyd Trimmell aka HiTechCoach via AccessMonster.com" <u14500@uwe> wrote in
message news:7c3433c66efd9@uwe...
>A primary key is a SINGLE field used as the record identifier. It really
> should have no meaning to the user and in most cases never seam by users.
>
> In all the databases that have worked with the have multiple fields for a
> primary key have made it a lot harder to do anything, even things that
> should
> be simple. I would never create one that way. I probably am glad the
> there
> are people that recommend it (like Blue Claw) or actually do it so that I
> will get lots of work fixing the issues it causes.
>
> --
> Boyd Trimmell
> aka HiTechCoach
> http://www.hitechcoach.com
> http://www.officeprogramming.com
>
> Message posted via AccessMonster.com
> http://www.accessmonster.com/Uwe/For...esign/200712/1
>

On Tue, 04 Dec 2007 17:58:20 -0600, Michael Gramelspacher <(E-Mail Removed)>
wrote:

>
>This works for me. It seems to go against what you are saying.
>
>Sub CreateTest()
>With CurrentProject.Connection
>
>.Execute _
>"CREATE TABLE Cities" & _
>" (city_id IDENTITY (1,1) NOT NULL UNIQUE" & _
>",city_name VARCHAR (30) NOT NULL" & _
>",PRIMARY KEY (city_name));"
>
>.Execute _
>"CREATE TABLE States" & _
>" (state_id IDENTITY(1,1) NOT NULL UNIQUE" & _
>",state_name VARCHAR (30) NOT NULL" & _
>",PRIMARY KEY (state_name));"
>
>.Execute _
>" CREATE TABLE Locations" & _
>" (location_id IDENTITY (1,1) NOT NULL UNIQUE" & _
>",city_id INTEGER NOT NULL" & _
>" REFERENCES Cities (city_id)" & _
>",state_id INTEGER NOT NULL" & _
>" REFERENCES States (state_id)" & _
>",PRIMARY KEY (city_id, state_id));"
>
>End With
>End Sub

Well, sure, it works. You're creating autonumber primary keys. It *works*,
everyone agrees with that; the question would be is it the *only* way that
works, or even the *best* way? Many would disagree.

In one particular case I'd really have to disagree with you. The US and
Canadian postal services have defined unique, stable (well *almost* stable),
short two-letter state codes. My States table would be more like

..Execute _
"CREATE TABLE States" & _
" (state_code CHAR(2) NOT NULL UNIQUE" & _
",state_name VARCHAR (30) NOT NULL" & _
",PRIMARY KEY (state_code));"


As for making the city_name or state_name the primary key of its table...
state_name you can get away with but certainly not city_name; there are many
cities named Springfield, and New Mexico even has two towns named Los Alamos
(the famous one with the rad lab, and a tiny village north of Las Vegas - no,
not the one in Nevada).

John W. Vinson [MVP]