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Hibernate Mapping problem because no primary key in database

 
Ehrenfrids Murzello
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I have a table which has no primary key. How to create the hibernate mapping xml without using the generator id
 
Edwin Keeton
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Every relational table has a "natural" primary key. However, it may be unrecognized and undefined. The best solution to your problem then is to determine what the primary key is and define it as such in your RDBMS.

Having said that, it is better to use a surrogate key for the primary key to protect against business semantics changes in the natural key. So why not use a generated id?
 
Paul Sturrock
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Edwin Keeton's suggestion is good. Using a surrogate makes perfect sense; fix the invalid data model so it truly represents relational data.

However, if you cannot change the data model, you can map the entire table as one big composite key. A horrible solution, but a work around which gives you time to fire the DBA who modelled your data this way, and hire a competent replacement.
 
Mark Spritzler
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"Ehrenfrids"-
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Sonny Gill
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Originally posted by Ehrenfrids:
I have a table which has no primary key. How to create the hibernate mapping xml without using the generator id


How are you accessing records in that table when not using Hibernate? i.e. when you use SQL directly.
 
Leticia Barbalho
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Well, when you don't have a primary key and want to access a specific row, I suppose your query will contain all fields, right? So, as weird as it may seem, you could use a composite-key with all fields in it.
 
Leticia Barbalho
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Now, that's for a key not using the generator! For generating a value, you would have to create a field in the DB and use is as your PK.
 
Ionescu Victor
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The problem might not be so simple to adress. Suppose I work with a legacy database and I have a readonly table (imported from a back-office) and I don't want to access individual rows in that table (I want just to list the records obtained form a join).
So: I can't add surogate key (I can't change the database) and I don't have a natural (business) key.
What about that?
 
Paul Sturrock
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Originally posted by Ionescu Victor:
The problem might not be so simple to adress. Suppose I work with a legacy database and I have a readonly table (imported from a back-office) and I don't want to access individual rows in that table (I want just to list the records obtained form a join).
So: I can't add surogate key (I can't change the database) and I don't have a natural (business) key.
What about that?


See my earlier answer. That's the only work around you have available to you.
 
Gagan Bajpai
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Well, I've a legacy database. I don't care to have a IF/Primary key. is there a way? or Hibernate just takes away that option?
 
Gagan Bajpai
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I tried using a big composite key. Hibernate generates a column on MySql.In development, may be I can live with that, but not in production. I'm no expert on Hibernate but this should be easy.
 
Paul Sturrock
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I'm no expert on Hibernate but this should be easy

An Object-Relational Mapping tool can only be expected to map relational data. Data without a primary key it is not relational, so it should be no surprise it doesn't work.
 
Juan David Zuluaga
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As the table has no primary key, it should not be mapped as an entity.

You could use a named query to insert data instead of declaring an entity, and perform the insert from the dao.


 
Deepak JavaEtc
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ORM is to map relations through primary and foreign key to database. If you are not having those on tables then you can use, criteria search with HQL or SQL and populated fetched data into related objects. These objects can be used for further. Example can be found at http://www.deepakgaikwad.net/?p=448
 
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