[Libreoffice-bugs] [Bug 32958] query design: once a join has two fields, cannot go back to one field

[bugzilla-daemon at freedesktop.org]

https://bugs.freedesktop.org/show_bug.cgi?id=32958

Jochen <dr at jochenschiffers.de> changed:

           What    |Removed                     |Added
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             Status|UNCONFIRMED                 |NEEDINFO
     Ever Confirmed|0                           |1

--- Comment #6 from Jochen <dr at jochenschiffers.de> 2012-07-31 06:45:54 UTC ---
Hi Lionel,

On German discuss-ML we have discussed this bug. Our opinion is:  we lack the
sense for such a query.
You link two tables with 2 connections. Normally a table is connected to
another by the following way: primary key of the second table is a foreign key
of the first table. Example:
Table 1: "Name" - contains ID, first name, last name
Table 2: "Address" - contains ID, Street, City
To link the tables together in Table 1 is added the field "AnschriftID". This
field contents  the field "id" of table "address".
Based on this construction You make following:
Table 1: "Name" - contains ID, first name, last name
Table 2: "Address" - contains ID, street address, city, first name, last name
No key field of a first table is a foreign key in the second table. A
connection concerning unique values is only possible by as many links to the
second table.
You have to link "first name" with "first name" and "last Name" with "last
Name" and so on. This design requires double entries in the tables and is of
course subject to error, even if the entries correctly in the fields be made.
Finally, it may exist for example more people called "Peter Smith". Then you
produce existing two equal persons four records and existing three equal
persons nine records and so on.
May be Your problem is not a bug but a not correct using of the database.

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