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zdila
 Post subject: how to map table relation not using foreign key?
PostPosted: Wed Apr 13, 2005 5:57 am 
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Joined: Tue Apr 05, 2005 12:09 pm
Posts: 48
Location: Slovakia (SK), Košice (KE)
Hi

I have 2 tables - tab1 and tab2. tab1.ref1 is unique NOT FOREIGN KEY referencing to tab2.pk2 which is CAN'T BE A KEY because tab2.pk2 is only a part of composite primary key for tab2.

Code:
CREATE TABLE tab1 (
    pk1 INTEGER NOT NULL PRIMARY KEY,
    ref1 INTEGER NOT NULL UNIQUE,
    ...
);

CREATE TABLE tab2 (
    pk1 INTEGER NOT NULL (REFERENCES tab3 <- maybe irrelevant for this problem),
    pk2 INTEGER NOT NULL,
    ....,
    PRIMARY KEY (pk1, pk2)
);


I'd like to have:
Code:
class Tab1 {
    Ineger id;
    Tab2 tab2;
    ....
}

Please tell me something how to map this. Please, I beg you!
Martin
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jandries
 Post subject:
PostPosted: Wed Apr 13, 2005 6:26 am 
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Joined: Thu Oct 16, 2003 7:30 am
Posts: 21
Location: Brussels
You could try to:

1. Create a fake property mapping to tab2.pk2, with the insert and update attributes of the <property/> set to false.

2. Use the property-ref attribute of the <many-to-one/> element for the tab2 field of the Tab1 class.

Johan.
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mate
 Post subject:
PostPosted: Wed Apr 13, 2005 7:32 am 
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Joined: Thu Nov 13, 2003 2:55 am
Posts: 71
Location: Sweden
If tab2.pk2 is part of a composite key, it seems that your class model is wrong, since there may be more than one tab2 record per tab1 record.

I.e.
Code:
class Tab1 {
    Ineger id;
    List<Tab2> tab2s;
    ....
}


Either way, please read the reference documentation on how to map this.
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zdila
 Post subject:
PostPosted: Wed Apr 13, 2005 7:48 am 
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Joined: Tue Apr 05, 2005 12:09 pm
Posts: 48
Location: Slovakia (SK), Košice (KE)
Hi jandries

Thanks for your reply, you are the first while I've posted my problem three times here in different formulations with no response. Unfortunately I haven't understood you much. Please be so kind (you or anyone else) to complete my hibernating mapping:

Code:
<class name="Tab1" table="TAB1">
<id name="id" column="pk1">
  <generator class="native" />
</id>

?????
Please add the mapping to Tab2:
??? <many-to-one unique="true" name="tab2" column="ref1" class="Tab2" ...> ... doesn't work???

PS: I have two such properties in Tab1 - both are unique
?????

</class>

<class name="Tab2" table="TAB2">
<composite-id>
  <key-many-to-one name="pk1" column="pk1" class="TAB3" />
  <key-property name="pk2" column="pk2" />
</composite-id>

...
</class>

THANKS IN ADVANCE!
Martin
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zdila
 Post subject:
PostPosted: Wed Apr 13, 2005 7:55 am 
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Joined: Tue Apr 05, 2005 12:09 pm
Posts: 48
Location: Slovakia (SK), Košice (KE)
hi mate

This mapping should be unique therefore there is no need of collection. My problem is described in specific situation at http://forum.hibernate.org/viewtopic.php?t=940821. I can't do better DB design for that. If you can, please tell me how.

Thanks in advance.
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mate
 Post subject:
PostPosted: Wed Apr 13, 2005 8:19 am 
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Posts: 71
Location: Sweden
Personally, I would create different tables for title and description, with book_id + language_id as primary key in both (if not using synthetic keys).

Otherwise: what would be the value of your title/description Maps (with language as key)? Just a String or an object? There are no columns except the key columns in the schema at the link you provided...
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jandries
 Post subject:
PostPosted: Wed Apr 13, 2005 8:24 am 
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Joined: Thu Oct 16, 2003 7:30 am
Posts: 21
Location: Brussels
Try something like

Code:
<class name="Tab1" table="TAB1">
<id name="id" column="pk1">
  <generator class="native" />
</id>

<many-to-one name="tab2" class="Tab2" column="ref1" property-ref="fake"/>

</class>

<class name="Tab2" table="TAB2">
<composite-id>
  <key-many-to-one name="pk1" column="pk1" class="TAB3" />
  <key-property name="pk2" column="pk2" />
</composite-id>

<property name="fake" column="pk2" insert="false" update="false"/>

</class>


Sections 5.1.9 and 5.1.10 give you more details.
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zdila
 Post subject:
PostPosted: Wed Apr 13, 2005 8:39 am 
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Posts: 48
Location: Slovakia (SK), Košice (KE)
mate,

Thanks for reply. Yes, they should be Maps where language would be a key. Creating separate table would be clear, but I use translated messages on more places (three for now ;-) ) and creating new table for each such field would be expensive. Any better idea?

jandries

Thanks. But I'd be expecting <one-to-many> (or many-to-many ???) mapping, because I need Map. Sorry I didn't mention it on the begining very clearly :-/ ... see my discussion with mate and that link.
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mate
 Post subject:
PostPosted: Wed Apr 13, 2005 8:50 am 
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Posts: 71
Location: Sweden
zdila wrote:
Creating separate table would be clear, but I use translated messages on more places (three for now ;-) ) and creating new table for each such field would be expensive.

In what way expensive? We have 50+ tables for texts in different languages.
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zdila
 Post subject:
PostPosted: Wed Apr 13, 2005 9:27 am 
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Joined: Tue Apr 05, 2005 12:09 pm
Posts: 48
Location: Slovakia (SK), Košice (KE)
wow ... so there is no better way to implement this? If not, I'll accept it.

Just to be sure:
If I have eg. 3 tables and 1st table has 2 fields to be i18ned, 2nd has 3 such fields and 3rd has 1 such field then I must create 2 + 3 + 1 = 6 many-to-many relations (like table LineItem in chapter 23.3)?

Thanks
Martin
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mate
 Post subject:
PostPosted: Wed Apr 13, 2005 9:40 am 
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Joined: Thu Nov 13, 2003 2:55 am
Posts: 71
Location: Sweden
zdila wrote:
so there is no better way to implement this?

"Better" as in...? Fewer tables? Better performance? Clearer data model?

zdila wrote:
Just to be sure:
If I have eg. 3 tables and 1st table has 2 fields to be i18ned, 2nd has 3 such fields and 3rd has 1 such field then I must create 2 + 3 + 1 = 6 many-to-many relations (like table LineItem in chapter 23.3)?

That's probably what I would do.

The only alternative I see is to have a discriminator column in the message table that tells you what kind of message it is. MySQL example:
Code:
CREATE TABLE (
   book_id INT,
   type ENUM('TITLE','DESCRIPTION','FOO','BAR'),
   language_id INT,
   text TEXT,
   PRIMARY KEY(book_id, type, language_id)
)

And then you would use the where-attribute (such as where="type = 'TITLE'") in your mapping.
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zdila
 Post subject:
PostPosted: Wed Apr 13, 2005 9:49 am 
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Joined: Tue Apr 05, 2005 12:09 pm
Posts: 48
Location: Slovakia (SK), Košice (KE)
Thanks mate for your help and your afford. I'll try to do it that way. So I am little bit more clever again :-)
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