Thread: Lookup tables

Should lookup tables have a numeric FK column as well as the description column?

If so, how should I add an FK to the two lookup tables in my database?

TIA,

Rich

Should lookup tables have a numeric FK column as well as the description column?

If so, how should I add an FK to the two lookup tables in my database?

On Tue, 4 Feb 2025, Rob Sargent wrote:

> I would definitely add an Id for each of the looked up values. The code
> can use the Id (for the join or lookup) and the string value can safely be
> changed (think typo) without ripple effect.  It also prevents other tables
> from referencing the lookup witrh bogus values (those not in the lookup
> table)
>
> Unless your lookup tables are huge I would create a new table matching
> your current table but with an identity column and load from you original
> table.
> https://www.postgresql.org/docs/current/ddl-identity-columns.html

Thanks, Rob. Each lookup table has only a very few rows,

I'll make new tables today.

Regards,

Rich

On Tue, 4 Feb 2025, David G. Johnston wrote:

> Most do (have a surrogate PK) since it removes cascading updates and is a
> smaller value.
>
> Lots of alter tables and update queries.

David,

That's a good point.

Thanks,

Rich

On Tue, Feb 4, 2025 at 9:41 AM David G. Johnston <david.g.johnston@gmail.com> wrote:

On Tuesday, February 4, 2025, Rich Shepard <rshepard@appl-ecosys.com> wrote:

Should lookup tables have a numeric FK column as well as the description column?

If so, how should I add an FK to the two lookup tables in my database?

Most do (have a surrogate PK) since it removes cascading updates

 

How does a synthetic PK "remove cascading updates"?  Doesn't the decision on whether or not to cascade update depend on the ON UPDATE CASCADE clause of the FK definition?

On Tue, Feb 4, 2025 at 9:28 AM Rich Shepard <rshepard@appl-ecosys.com> wrote:

Should lookup tables have a numeric FK column as well as the description column?

Does your lookup table just have one column?  (That's what your question seems to imply, but that makes no sense, since the whole point of a lookup table is to store some sort of a code in the "child" table instead of the whole text of the description.)

On Tue, 4 Feb 2025, Ron Johnson wrote:

> Does your lookup table just have one column?  (That's what your question
> seems to imply, but that makes no sense, since the whole point of a lookup
> table is to store some sort of a code in the "child" table instead of the
> whole text of the description.)

Ron,

Yes, each has a single column of type names, industrytypes and statustypes.
I've always used the descriptive names in queries.

Rich

On Tue, 4 Feb 2025, David G. Johnston wrote:

> The point of a lookup table is to provide a unique list of authoritative
> values for some purpose. Kinda like an enum. But having the label serve as
> the unique value is reasonable - we only add surrogates for optimization.

David,

The industrytypes table has 26 rows, the statustypes table has 8 rows. Your
explanation suggests that for this database adding a PK to each table adds
little, if anything.

Regards,

Rich

On Tue, 4 Feb 2025, David G. Johnston wrote:

The point of a lookup table is to provide a unique list of authoritative
values for some purpose. Kinda like an enum. But having the label serve as
the unique value is reasonable - we only add surrogates for optimization.

David,

The industrytypes table has 26 rows, the statustypes table has 8 rows. Your
explanation suggests that for this database adding a PK to each table adds
little, if anything.

On Tue, 4 Feb 2025, David G. Johnston wrote:

> It’s the FK side where the cost savings are experienced.

David,

Okay.

Thanks,

Rich

On 2/4/25 07:19, Ron Johnson wrote:

> How big is the database?  A tiny 500MB db just for you can get by with 
> poor design.  (But then, why are you using PG instead of SQLite?)

For the reasons listed here:

https://sqlite.org/quirks.html

In particular:

[...]

2. SQLite Is Embedded, Not Client-Server

3. Flexible Typing

SQLite is flexible with regard to datatypes. Datatypes are advisory 
rather than mandatory.

4. Foreign Key Enforcement Is Off By Default

[...]

> 
> More importantly, will you ever update the descriptions?  Of course not! 
> Famous last words.  Having a separate PK means that you update one row 
> in one column, while what you've done means that tens/hundreds of 
> thousands of rows in possibly dozens of tables need to be updated.
> 
> It also means that *you* can easily change things in your ad hoc 
> database *without forgetting* to update a table.
> 
> This is called an "update anomaly" in relational design theory.
> 
> -- 
> Death to <Redacted>, and butter sauce.
> Don't boil me, I'm still alive.
> <Redacted> lobster!

-- 
Adrian Klaver
adrian.klaver@aklaver.com

> On 4 Feb 2025, at 15:27, Rich Shepard <rshepard@appl-ecosys.com> wrote:
>
> Should lookup tables have a numeric FK column as well as the description column?
>
> If so, how should I add an FK to the two lookup tables in my database?

I’ve read the whole thread and the reasoning for having (numeric) autogenerated surrogate key is:
a) performance
b) no cascading updates

I would like to add another dimension to this discussion: logical consistency.

Imagine the following simplified schema with surrogate PK:

create table restaurant (
  restaurant_id int not null primary key generated always as identity,
  name text not null unique
);
create table restaurant_visit (
  visit_id int not null primary key generated always as identity,
  guest_username text not null,
  when date not null,
  restaurant_id not null foreign key restaurant(restaurant_id),
  rating smallint not null
);

Let’s say users on your website register restaurant visits and rate them.

The query to register a visit is:
insert into restaurant_visit
select $user, current_date, restaurant_id, $rating
from restaurant where name = $restaurant_name


It is now completely unclear what it means to change the name of the restaurant for already registered visits.
Is it still the same restaurant with a different name or a different restaurant?

Or let say someone swaps names of two restaurants.
That means a user that goes to the same restaurant every day would register visits to two different restaurants!

Using the name of a restaurant as primary key gets rid of these logical anomalies because
the database model now reflects facts from reality.

Having surrogate keys makes your relational database more like a network/object oriented database where rows don’t
representfacts but rather some entities that have identity independent from their attributes. 

Thanks,
Michal

Am Tue, Feb 04, 2025 at 05:31:13PM +0100 schrieb Michał Kłeczek:

> It is now completely unclear what it means to change the name of the restaurant for already registered visits.
> Is it still the same restaurant with a different name or a different restaurant?
>
> Or let say someone swaps names of two restaurants.
> That means a user that goes to the same restaurant every day would register visits to two different restaurants!
>
> Using the name of a restaurant as primary key gets rid of these logical anomalies because
> the database model now reflects facts from reality.

Reality tends to become so ambiguous as to not be
reflectable (two entirely different restaurants eventually,
within the flow of time, carry the very same name).

A primary key is very likely not the proper place to reflect
arbitrary business logic (is it the same restaurant or not ?
what if two restaurants have the same name at the same time
?). Primary keys are tools at the technical level.

Karsten
--
GPG  40BE 5B0E C98E 1713 AFA6  5BC0 3BEA AC80 7D4F C89B

On 2/4/25 09:51, Karsten Hilbert wrote:
> Am Tue, Feb 04, 2025 at 05:31:13PM +0100 schrieb Michał Kłeczek:
>
>> It is now completely unclear what it means to change the name of the restaurant for already registered visits.
>> Is it still the same restaurant with a different name or a different restaurant?
>>
>> Or let say someone swaps names of two restaurants.
>> That means a user that goes to the same restaurant every day would register visits to two different restaurants!
>>
>> Using the name of a restaurant as primary key gets rid of these logical anomalies because
>> the database model now reflects facts from reality.
> Reality tends to become so ambiguous as to not be
> reflectable (two entirely different restaurants eventually,
> within the flow of time, carry the very same name).
>
> A primary key is very likely not the proper place to reflect
> arbitrary business logic (is it the same restaurant or not ?
> what if two restaurants have the same name at the same time
> ?). Primary keys are tools at the technical level.
>
> Karsten
> --
> GPG  40BE 5B0E C98E 1713 AFA6  5BC0 3BEA AC80 7D4F C89B
>
>
That OP is using a single column is interesting:  Taking this notion to 
the restaurant/visit theme, the list of names or restaurants becomes a 
proper table 'restaurant' (name, addresss, phone, website, etc).  The 
name is as useless as a key as first/last is for person.

On Tue, Feb 4, 2025 at 11:31 AM Michał Kłeczek <michal@kleczek.org> wrote:

[snip] 

The query to register a visit is:
insert into restaurant_visit
select $user, current_date, restaurant_id, $rating
from restaurant where name = $restaurant_name


It is now completely unclear what it means to change the name of the restaurant for already registered visits.
Is it still the same restaurant with a different name or a different restaurant?

Or let say someone swaps names of two restaurants.
That means a user that goes to the same restaurant every day would register visits to two different restaurants!

Valid concerns, which means that you add a new restaurant record when the name changes.

> On 4 Feb 2025, at 17:51, Karsten Hilbert <Karsten.Hilbert@gmx.net> wrote:
>
> Am Tue, Feb 04, 2025 at 05:31:13PM +0100 schrieb Michał Kłeczek:
>
>> It is now completely unclear what it means to change the name of the restaurant for already registered visits.
>> Is it still the same restaurant with a different name or a different restaurant?
>>
>> Or let say someone swaps names of two restaurants.
>> That means a user that goes to the same restaurant every day would register visits to two different restaurants!
>>
>> Using the name of a restaurant as primary key gets rid of these logical anomalies because
>> the database model now reflects facts from reality.
>
> Reality tends to become so ambiguous as to not be
> reflectable (two entirely different restaurants eventually,
> within the flow of time, carry the very same name).
>
> A primary key is very likely not the proper place to reflect
> arbitrary business logic (is it the same restaurant or not ?
> what if two restaurants have the same name at the same time

These are of course problems ( and beyond the scope of my contrived example ).

The point is though, that having surrogate PK not only does not solve these issues but makes them worse by kicking the
candown the road and allowing for inconsistencies. 


—
Michał

> On 4 Feb 2025, at 18:27, Thiemo Kellner <thiemo@gelassene-pferde.biz> wrote:
>
>  Unless the lookup table is actually a check constraint one can use to populate dropdown boxes in an interface.

That is even worse because it ceases being transactional and users might select something different than what they see
onthe screen. 

—
Michał

Am Tue, Feb 04, 2025 at 06:30:53PM +0100 schrieb Michał Kłeczek:

> > On 4 Feb 2025, at 18:27, Thiemo Kellner <thiemo@gelassene-pferde.biz> wrote:
> >
> >  Unless the lookup table is actually a check constraint one can use to populate dropdown boxes in an interface.
>
> That is even worse because it ceases being transactional and users might select something different than what they
seeon the screen. 

I never thought of that, thanks.

Karsten
--
GPG  40BE 5B0E C98E 1713 AFA6  5BC0 3BEA AC80 7D4F C89B

> On 4 Feb 2025, at 18:27, Thiemo Kellner <thiemo@gelassene-pferde.biz> wrote:
>
>  Unless the lookup table is actually a check constraint one can use to populate dropdown boxes in an interface.

That is even worse because it ceases being transactional and users might select something different than what they see on the screen.

04.02.2025 18:31:09 Michał Kłeczek <michal@kleczek.org>:

>>  Unless the lookup table is actually a check constraint one can use to populate dropdown boxes in an interface.
>
> That is even worse because it ceases being transactional and users might select something different than what they
seeon the screen. 

In how far is a real check constraint less transactional? And in how far is it more advisable to have a real check
constraintand fill your dropdown boxes from another source and having to keep that source on sync with the real check
constraint?

On Tue, 4 Feb 2025, Rob Sargent wrote:

> Unless your lookup tables are huge I would create a new table matching
> your current table but with an identity column and load from you original
> table.

I created a new table:

create table ind_types_lu (
   ind_nbr serial primary key,
   ind_name varchar(32) not null
);

Now the database has the new table and a new sequence:

  public | ind_types_lu             | table    | rshepard
  public | ind_types_lu_ind_nbr_seq | sequence | rshepard

I want to replace the old lookup table (with no FK) with this one. Can I
use:

alter table rename ind_types_lu to industrytypes;

and have the sequence name changed, too?

TIA,

Rich

I want to replace the old lookup table (with no FK) with this one.

On Tue, 4 Feb 2025, David G. Johnston wrote:


> Is the use of FK here intentional or a typo?

Sigh, typo. Should be PK.

Rich

On Tue, 4 Feb 2025, Rich Shepard wrote:

> I'll make new tables today.

That did not work as well as I expected. Instead, I added a new column (type
`serial') to each of the two lookup tables. That adds a PK to each while
retaining the table and column names referenced by other tables.

Thanks for all your comments,

Rich

04.02.2025 18:31:09 Michał Kłeczek <michal@kleczek.org>:

>
>> On 4 Feb 2025, at 18:27, Thiemo Kellner <thiemo@gelassene-pferde.biz> wrote:
>>
>>  Unless the lookup table is actually a check constraint one can use to populate dropdown boxes in an interface.
>
> That is even worse because it ceases being transactional and users might select something different than what they
seeon the screen. 

I might see what you want to point out. E.g. the table is COLOURS. The rec with id 1 is RED, the one with id 2 is BLUE,
3is GREE and so on. Now you load these values into the dropdown box that sports RED, BLUE, GREE and so on. While
someoneselects GREE, there is a maintenance release changing GREE to YELLOW. So when that someone sends the selection
byid to the backend, not GREE is selected but YELLOW. 

A) Your release changed the sementics of the record 3. It's meaning changed. I cannot recommend doing that.
B) If you absolutely must change the semantic, put your application into maintenance mode in which noone can select
anythingbeforehand. 

If the maintenance would just correct the typo from GREE to GREEN, nothing would happen. Yor customer still ordered the
lavishlygreen E-Bike her hear ever desired. 

Am Tue, Feb 04, 2025 at 10:41:38PM +0100 schrieb Thiemo Kellner:

> >> On 4 Feb 2025, at 18:27, Thiemo Kellner <thiemo@gelassene-pferde.biz> wrote:
> >>
> >>  Unless the lookup table is actually a check constraint one can use to populate dropdown boxes in an interface.
> >
> > That is even worse because it ceases being transactional and users might select something different than what they
seeon the screen. 
>
> I might see what you want to point out. E.g. the table is COLOURS. The rec with id 1 is RED, the one with id 2 is
BLUE,3 is GREE and so on. Now you load these values into the dropdown box that sports RED, BLUE, GREE and so on. While
someoneselects GREE, there is a maintenance release changing GREE to YELLOW. So when that someone sends the selection
byid to the backend, not GREE is selected but YELLOW. 

Yep, that's what I meant and which I never thought of before.

Karsten
--
GPG  40BE 5B0E C98E 1713 AFA6  5BC0 3BEA AC80 7D4F C89B

> On 4 Feb 2025, at 22:41, Thiemo Kellner <thiemo@gelassene-pferde.biz> wrote:
>
> 04.02.2025 18:31:09 Michał Kłeczek <michal@kleczek.org>:
>
>>
>>> On 4 Feb 2025, at 18:27, Thiemo Kellner <thiemo@gelassene-pferde.biz> wrote:
>>>
>>>  Unless the lookup table is actually a check constraint one can use to populate dropdown boxes in an interface.
>>
>> That is even worse because it ceases being transactional and users might select something different than what they
seeon the screen. 
>
> I might see what you want to point out. E.g. the table is COLOURS. The rec with id 1 is RED, the one with id 2 is
BLUE,3 is GREE and so on. Now you load these values into the dropdown box that sports RED, BLUE, GREE and so on. While
someoneselects GREE, there is a maintenance release changing GREE to YELLOW. So when that someone sends the selection
byid to the backend, not GREE is selected but YELLOW. 
>
> A) Your release changed the sementics of the record 3. It's meaning changed. I cannot recommend doing that.

That’s what using natural keys and FK’s restricting their changes guarantee: no (accidental) changes to meaning of
data.
Even with cascading updates you still have transactional semantics (ie. the user selects what’s on the screen or gets
anerror). 

> B) If you absolutely must change the semantic, put your application into maintenance mode in which noone can select
anythingbeforehand. 

All this error prone hassle and downtime can be avoided with natural keys and guarantees that DBMS gives you.

>
> If the maintenance would just correct the typo from GREE to GREEN, nothing would happen. Yor customer still ordered
thelavishly green E-Bike her hear ever desired. 

The question is: how do you _ensure_ that?

—
Michal

On Tue, Feb 4, 2025 at 9:31 AM Michał Kłeczek <michal@kleczek.org> wrote:

Well, we were talking about lookup tables and not entity modelling...

Having surrogate keys makes your relational database more like a network/object oriented database where rows don’t represent facts but rather some entities that have identity independent from their attributes.

My identity is separate from any single value of my attributes.  Basically any single thing about me can be changed but the coherent existence of my "self" remains the same.

Frankly, the restaurant example the "Owner" of the business should probably be considered part of its primary key - they don't announce "under new ownership/management" just for fun - the new owner wants to keep the brand recognition but discard historical opinions that are likely no longer true.

El 04-02-25 a las 18:08, Michał Kłeczek escribió:
>> Reality tends to become so ambiguous as to not be
>> reflectable (two entirely different restaurants eventually,
>> within the flow of time, carry the very same name).
>>
>> A primary key is very likely not the proper place to reflect
>> arbitrary business logic (is it the same restaurant or not ?
>> what if two restaurants have the same name at the same time
> These are of course problems ( and beyond the scope of my contrived example ).
>
> The point is though, that having surrogate PK not only does not solve these issues but makes them worse by kicking
thecan down the road and allowing for inconsistencies.
 
Only if you do not see the primary key as the main immutable value 
identifying an object, entity, you name it. Having said that, it is very 
questionable that a natural key (names to name one) can be a suitable 
primary key (think of typo).

> On 5 Feb 2025, at 19:07, Thiemo Kellner <thiemo@gelassene-pferde.biz> wrote:
>
> El 04-02-25 a las 18:08, Michał Kłeczek escribió:
>>> Reality tends to become so ambiguous as to not be
>>> reflectable (two entirely different restaurants eventually,
>>> within the flow of time, carry the very same name).
>>>
>>> A primary key is very likely not the proper place to reflect
>>> arbitrary business logic (is it the same restaurant or not ?
>>> what if two restaurants have the same name at the same time
>> These are of course problems ( and beyond the scope of my contrived example ).
>>
>> The point is though, that having surrogate PK not only does not solve these issues but makes them worse by kicking
thecan down the road and allowing for inconsistencies. 
> Only if you do not see the primary key as the main immutable value identifying an object, entity, you name it.

Surrogate key cannot identify any (real) object by definition :)
What object is identified by PK value 42 in “restaurants” table?

> Having said that, it is very questionable that a natural key (names to name one) can be a suitable primary key (think
oftypo). 

Typos are indeed a problem but adding surrogate key does not solve it, I’m afraid.

—
Michal

El 05-02-25 a las 19:13, Michał Kłeczek escribió:
>> Only if you do not see the primary key as the main immutable value identifying an object, entity, you name it.
> Surrogate key cannot identify any (real) object by definition :)
> What object is identified by PK value 42 in “restaurants” table?
What object is identified by a PK value "löasidfhaösliw" in a restaurant 
table? It is the context only giving it sense and not less sense then 42 
or "Pizza Hut". In fact on disk, you won't even find 42 or "Pizza Hut". 
On hard disks, e.g., it is the direction of a magnetic field of several 
locations on the disk. Btw, 42 seems to me a quite geeky name for a nerd 
restaurant.
>> Having said that, it is very questionable that a natural key (names to name one) can be a suitable primary key
(thinkof typo).
 
> Typos are indeed a problem but adding surrogate key does not solve it, I’m afraid.
In how far does it not solve it? Or maybe better asked. Is your problem 
that typos occur or is the problem the amount of hassle to fix it?

El 05-02-25 a las 13:55, Michał Kłeczek escribió:
>> A) Your release changed the sementics of the record 3. It's meaning changed. I cannot recommend doing that.
> That’s what using natural keys and FK’s restricting their changes guarantee: no (accidental) changes to meaning of
data.
> Even with cascading updates you still have transactional semantics (ie. the user selects what’s on the screen or gets
anerror).
 
Sorry, that is utter nonsense. You cannot ever guarantee an update does 
not mess up the semantics on the updated field, change the meaning. You 
would need a check constraint which in it turn needs to get set up where 
one can mess up things.
>> B) If you absolutely must change the semantic, put your application into maintenance mode in which noone can select
anythingbeforehand.
 
> All this error prone hassle and downtime can be avoided with natural keys and guarantees that DBMS gives you.
And I thought you would have denied the need of changing semantics 
above. And no, changing your natural keys semantically ALWAYS requires 
downtime to make sure you do not run into the race condition described 
above.
>> If the maintenance would just correct the typo from GREE to GREEN, nothing would happen. Yor customer still ordered
thelavishly green E-Bike her hear ever desired.
 
> The question is: how do you _ensure_ that?
Ensure, the update goes from GREE to GREEN? You cannot, simple as that. 
You just can minimize the risk by testing, testing, testing. But that 
holds equally true for the business key of a surrogate key table as 
natural key table. That's why the surrogate key is such an elegant 
construct. You can change business key of the record with id 3 from GREE 
to GREEN, VERT, GRÜN, VERDE or ASéLDHK()*NSLDFHP)(*Z . It keeps its 
meaning of the perception of the human eye of electromagnetic waves of 
the wavelength roughly between 495-570 nm (according to Wikipedia).

> On 5 Feb 2025, at 21:33, Thiemo Kellner <thiemo@gelassene-pferde.biz> wrote:
>
>
> El 05-02-25 a las 13:55, Michał Kłeczek escribió:
>>> A) Your release changed the sementics of the record 3. It's meaning changed. I cannot recommend doing that.
>> That’s what using natural keys and FK’s restricting their changes guarantee: no (accidental) changes to meaning of
data.
>> Even with cascading updates you still have transactional semantics (ie. the user selects what’s on the screen or
getsan error). 
> Sorry, that is utter nonsense. You cannot ever guarantee an update does not mess up the semantics on the updated
field,change the meaning. Y 

But you can guarantee that if you change the value of the key after the user displays it - the user will get an error
onsubmission (whereas with the surrogate key it would happily proceed without user noticing). 

> ou would need a check constraint which in it turn needs to get set up where one can mess up things.
>>> B) If you absolutely must change the semantic, put your application into maintenance mode in which noone can select
anythingbeforehand. 
>> All this error prone hassle and downtime can be avoided with natural keys and guarantees that DBMS gives you.
> And I thought you would have denied the need of changing semantics above. And no, changing your natural keys
semanticallyALWAYS requires downtime to make sure you do not run into the race condition described above. 

How so? The user is going to get FK violation - you do not need any downtime to make sure users don’t submit wrong
values.

>>> If the maintenance would just correct the typo from GREE to GREEN, nothing would happen. Yor customer still ordered
thelavishly green E-Bike her hear ever desired. 
>> The question is: how do you _ensure_ that?
> Ensure, the update goes from GREE to GREEN? You cannot, simple as that. You just can minimize the risk by testing,
testing,testing. 

You can also simply disallow updates with FK constraint eliminating risk.

> But that holds equally true for the business key of a surrogate key table as natural key table. That's why the
surrogatekey is such an elegant construct. You can change business key of the record with id 3 from GREE to GREEN,
VERT,GRÜN, VERDE or ASéLDHK()*NSLDFHP)(*Z . It keeps its meaning of the perception of the human eye of electromagnetic
wavesof the wavelength roughly between 495-570 nm (according to Wikipedia). 

And why do you think unconstrained updating of business key is a good thing?
You must implement rules governing what can and what cannot be changed *somewhere* - not doing it in the database means
youhave to do it in applications. 

Anyway - let’s agree to disagree :)

—
Michal

El 05-02-25 a las 22:19, Michał Kłeczek escribió:
> But you can guarantee that if you change the value of the key after the user displays it - the user will get an error
onsubmission (whereas with the surrogate key it would happily proceed without user noticing).
 
As you very rightly say happily proceed, because that is, what you 
actually want. The user chose GREE meaning green, which is updated in 
the meantime to GREEN. All good. Your solution throws an error for nothing.
> How so? The user is going to get FK violation - you do not need any downtime to make sure users don’t submit wrong
values.
Sorry, I was not aware, your aim is to bother the customer with FK 
violation messages, if you can avoid it.
>> Ensure, the update goes from GREE to GREEN? You cannot, simple as that. You just can minimize the risk by testing,
testing,testing.
 
> You can also simply disallow updates with FK constraint eliminating risk.
This is nothing that is specific to surrogate or natural keys. If one 
disallow updates, one has to live with typos and everything.
>> But that holds equally true for the business key of a surrogate key table as natural key table. That's why the
surrogatekey is such an elegant construct. You can change business key of the record with id 3 from GREE to GREEN,
VERT,GRÜN, VERDE or ASéLDHK()*NSLDFHP)(*Z . It keeps its meaning of the perception of the human eye of electromagnetic
wavesof the wavelength roughly between 495-570 nm (according to Wikipedia).
 
> And why do you think unconstrained updating of business key is a good thing?
I am not sure what is your take on "unconstrained". As already 
mentioned, testing is the only constraint you can set up. And I am 
neither sure where your problem is with updating unless you have an 
update orgy because your ref-constraint goes on natural keys.
> You must implement rules governing what can and what cannot be changed *somewhere* - not doing it in the database
meansyou have to do it in applications.
 
That sounds adventurous. Maybe I am not seeing what you mean, but is 
sound to me that you build a shadow database where you map your GREE to 
GREEN in the application layer so the application can display the 
correct value in the GUI, but no one has to update the core database. 
And if there is a typo in the shadow data base you build another mapping 
database on top of it?
> Anyway - let’s agree to disagree :)
Agreed :-)

06.02.2025 22:04:34 Peter J. Holzer <hjp-pgsql@hjp.at>:

>> I might see what you want to point out. E.g. the table is COLOURS. The
>> rec with id 1 is RED, the one with id 2 is BLUE, 3 is GREE and so on.
>> Now you load these values into the dropdown box that sports RED, BLUE,
>> GREE and so on. While someone selects GREE, there is a maintenance
>> release changing GREE to YELLOW. So when that someone sends the
>> selection by id to the backend, not GREE is selected but YELLOW.
>
> I fail to see why use of a surrogate key is the problem here.

It seems I did not make mys of clear. I don't see either and don' remember an occasion in over 20 years of DWH business
theuse of surrogates was a problem.
 

> Either changing the color from GREE to YELLOW makes sense or it doesn't.

Hear, hear.

> If it doesn't make sense, then it's release which is faulty, not the
> model.

ACK

Thiemo