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Posted to ojb-user@db.apache.org by Abid Hussain <ab...@abid76.de> on 2006/05/12 17:14:29 UTC

updating the primary key of a table row

Hi everybody,

i wonder how to perform an update on a table where i changed the primary 
key.

Let's say i've got a table, where the only unique column is the primary 
key itself - like this:
CREATE TABLE foo (

	foo_name VARCHAR PRIMARY KEY
);

Now I change the column foo_name of a row from 'bla' to 'blub' and 
perform an update.
In SQL, I would do this:
UPDATE foo SET foo_name = 'blub' WHERE foo_name = 'bla';

When using OJB I would first retrieve the object I want to update:
Foo foo = new Foo();
foo.setFooName("bla");
Query q = new QueryByIdentity(foo);
foo = (Foo) broker.getObjectByQuery(q);

Then set the attribute fooName:
foo.setFooName("blub");)

Then perform update:
broker.store(foo, ObjectModification.UPDATE);

But how should OJB identify the object which is to be updated? I just 
have changed the primary key and there are not other unique columns!

Any ideas?

Regards,

Abid Hussain


-- 

Abid Hussain
Mail: abid.hussain@abid76.de
Web: http://www.abid76.de

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Re: updating the primary key of a table row

Posted by Abid Hussain <ab...@abid76.de>.
Hi Armin,

> For this special case you have to delete the old value/obj and then 
> insert the new vale/obj.
> 
> regards,
> Armin

thanks a lot. I thought of this possibility, but wondered if there is 
another way to perform the update.

Regards,

Abid

-- 

Abid Hussain
Mail: abid.hussain@abid76.de
Web: http://www.abid76.de

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Re: updating the primary key of a table row

Posted by Armin Waibel <ar...@apache.org>.
Hi Abid,

Abid Hussain wrote:
> Hi everybody,
> 
> i wonder how to perform an update on a table where i changed the primary 
> key.

You can't change a PK value in OJB and at least OJB needs one PK field.

> 
> Let's say i've got a table, where the only unique column is the primary 
> key itself - like this:
> CREATE TABLE foo (
> 
>     foo_name VARCHAR PRIMARY KEY
> );

For this special case you have to delete the old value/obj and then 
insert the new vale/obj.

regards,
Armin

> 
> Now I change the column foo_name of a row from 'bla' to 'blub' and 
> perform an update.
> In SQL, I would do this:
> UPDATE foo SET foo_name = 'blub' WHERE foo_name = 'bla';
> 
> When using OJB I would first retrieve the object I want to update:
> Foo foo = new Foo();
> foo.setFooName("bla");
> Query q = new QueryByIdentity(foo);
> foo = (Foo) broker.getObjectByQuery(q);
> 
> Then set the attribute fooName:
> foo.setFooName("blub");)
> 
> Then perform update:
> broker.store(foo, ObjectModification.UPDATE);
> 
> But how should OJB identify the object which is to be updated? I just 
> have changed the primary key and there are not other unique columns!
> 
> Any ideas?
> 
> Regards,
> 
> Abid Hussain
> 
> 

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