Re: [libreoffice-users] LO 4.0: intrinsic database: relations only between primaries keys?

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On 02/11/2013 09:18 AM, Uwe Brauer wrote:
> Hello
>
> (It seems that my message did not pass to the gmane newserver, that is
> why I resend this message)
>
> I am using Kubuntu 10.04 and installed the latest LO 4.0 (the problem
> occurs also in 3.6, and in OO 3.3).
>
> I set up the intrinsic (hsql) data base. I created two tables using the
> templates: one is Task (from business) the other Accounts (from
> personal). All the field values are the default ones.  I use an existing
> field as a primary key (autovalue on), namely TaskId (numeric) and
> AccountId (numeric). I insert some data and save them.
>
>
> I then set up a relation between the two tables, where I relate the
> fields corresponding to the primary keys. (TaskId-->AccountId) I save
> the relation and reopen it.
>
> Now I want to edit the relation and I am offered the possibility to add
> more fields. So I select the notes file in either table but I receive
> the following error.
>
>   Primary or unique constraint required on main table.
>   "Accounts" in statement [ALTER TABLE "Tasks"
>    ADD FOREIGN KEY ("TaskId","Notes") REFERENCE "Accounts"("AccountI","Notes")]
>   
> I am puzzled, in the intrinsic database only relations between primary
> keys are possible?? Is this a property of the intrinsic database, or is it a
> bug? I am thinking of submitting a bug report.
>
> Any help would be appreciated
>
> Uwe Brauer
     How do you define an "intrinsic database"? I do not understand the 
term.
     Primary-foreign key pairs are created when a table is normalized. 
(There several levels of normalized tables.) These pairs are based upon 
the relationships between the fields of the original table.
     So, you probably should put all the fields of the two tables into 
a single table with the exception of any fields that belong to both 
tables. For example the single table contains only one primary key 
("ID") and one field named "Notes". Then look for any fields (other than 
"ID") that determine the values of other fields. (In other words, begin 
to normalize the table.) Without knowing all of the fields that you are 
using, it would be difficult to know what fields these might be.
     FYI, very seldom will two tables have a 1:1 relationship (linking 
the primary keys of the two tables). Very likely, yours doesn't either. 
Most often, these relationships involve a primary key of one table and a 
foreign key of the other.

--Dan

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