Re: Compare with default value?

Hi,

Am 13.03.21 um 22:21 schrieb Tim Cross:
>
> Ulrich Goebel <ml(at)fam-goebel(dot)de> writes:
>
>> Hi,
>>
>> o.k. I have to give some more information...
>>
>> Am 13.03.21 um 19:39 schrieb David G. Johnston:
>>> On Saturday, March 13, 2021, Ulrich Goebel <ml(at)fam-goebel(dot)de
>>> <mailto:ml(at)fam-goebel(dot)de>> wrote:
>>>
>>> I would like to get the rows, where a column has the default value,
>>> similar to:
>>> select id fromt tbl where col = default
>>>
>>> If the default is a simple constant then why go through the trouble instead of
>>> just writing col = ‘constant’ ?
>>
>
> I think you may need to re-think your design or at least come at it from
> a different perspective. As shown by another post in the thread, at some
> level, this is 'sort of' possible, but it will be ugly and fragile.

Yes, I am re-thinking allredy...

>
> Possibly one of the issues you have is on one hand, you want the
> solution to be as generic as possible, but on the other, you require it
> to have specific knowledge about the definition of your table. i.e.
> which column(s) have a default value. Furthermore, your 'completion'
> table will need to be defined based on this information i.e. potentially
> multiple columns with multiple different data types etc.
>
> While the additional information you provided does give some increased
> understanding of what your trying to do, it is still describing your
> desired solution implementation. It might be better if you provide more
> high level details of what your attempting to do so that we can better
> understand how you arrived at the proposed solution and whether there
> may be better alternatives available.

o.k.: For a conference I have a tbl_person which holds all peoble which
are involved: participants and people which provide private lodgins for
other participants. (There are much more roles, but for illustration
these two should be enough.) Of course each person can have one or more
roles at the conference, a n-n-relation models that. Now our workflow
allows that one person find it way in the tbl_person twice (ore even
more often): for example the conference office generates a row for Tom,
because he provides private lodgin. Later on Tom decides to participate
an fills the online registration formular. These data generate the
second row for Tom. Both rows hold significant information which the
other doesn't hold. Let's say the online register gave the birthday, the
other holds information about the lodgin (bed with or without
breakfast). The next step then is that the conference office get notice
of the doubled person an should make one row out of the existing two
rows. The office decide which of the two rows should be completed with
data from the other row. Therefore I would like to pick the columns in
the first row where we have default values and replace it by the value
from the second row.

There are more ways to end with two or even more rows per person. May be
it would have been much better to avoid these possibilities. But for the
moment I have a given database structure running in productive mode, so
it is not easy to re-structure the structure or even the workflows...

Thanks for patience reading all that!

--
Ulrich Goebel
Am Büchel 57, 53173 Bonn