> Not at the moment, but my memory is telling me that I *have* seen such
> things before.

I too could have sworn that I'd come across alphanumeric codes several
times. But when trying to remember and search for specific examples I
couldn't come up with any.

Maybe alphanumerics are more common in fields other than computing, e.g.
various kinds of catalogs, and our brains mix up those domains.
Computers make it easy to deal with integers so we usually use those.
And where letters can be used, it's usually as easy to spell out
complete words as it is to use cryptic codes.

> Anyway, SQLSTATEs are (a) part of the SQL standards,
> although private-use extensions are allowed, and (b) can be in a
> one-to-many relationship with db-specific numbers and ids.  So I'm okay
> with them now as a string-valued key specific to DBs.

Cool! Thanks for listening to the arguments.

> There is a list at <https://en.wikipedia.org/wiki/SQLSTATE>.

Yeah, those are the standard ones; specific databases can add their own.

The table on that Wikipedia page has several fields. Should we be
prepared with properties for all of them:

sqlstate
category
class-code
class-title
subclass-code
Subclass-title

>     'name is vague
>
> Good point.  +1 for 'id.

'id is also vague since we have a numeric and a mnemonic; both are a
kind of identifiers. In RnRS parlance, identifier ~= symbol, but this is
not universal. Generally an identifier is any magic datum that
identifies something; a number fits the bill.

Hence I'd still prefer 'number or 'code for the number and 'memonic for
the symbol.

SQLSTATE class codes can contain letters in addition to digits, so they
need to be 'class-code instead of 'class-number. Perhaps the generic
error number property can be 'code for symmetry with 'class-code.

How bad is 'mnemonic? It may be slightly torturous to spell for
non-native speakers, but probably palatable.

>     'message is more appropriate for statuses than 'title
>     (unless the error message is a whole essay that needs its own title).
>
> I would hope not!

Some databases' documentation says they can return really elaborate
errors, complete with troubleshooting tips and everything. But maybe the
thing they send as 'message is close enough to a title :)