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 Post subject: implicit join : theta or inner ?
PostPosted: Thu Dec 30, 2004 8:26 am 
Expert
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Joined: Thu Sep 04, 2003 8:23 am
Posts: 368
Hibernate version:
2.1.7

Hi,

In the chapter 7 of the book, on page 266, there is an explanation on implicit joins. In the example the hql query with implicit joins is translated with inner joins in the sql query.

But in the forum I found this gavin's post : http://forum.hibernate.org/viewtopic.ph ... icit+theta

In this post, gavin said that implicit joins are transalated in theta style joins but I cannot understand his explanation.

I did some tests with a relation like the cat's mate in the reference documentation. It seems that implicit joins are translated into theta style joins. Can you explain me why and can you tell me if it is an error in the book or if it depends on the circumstances ?

Thanx

Seb


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 Post subject:
PostPosted: Thu Dec 30, 2004 8:36 am 
Hibernate Team
Hibernate Team

Joined: Mon Aug 25, 2003 9:11 pm
Posts: 4592
Location: Switzerland
The example in the book is not Hibernate-generated SQL, but hand written for illustration purposes. For a human the normal join syntax is easier to understand. It shouldn't make any difference for the query optimizer, even the driving table is easy to determine in both cases.


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 Post subject:
PostPosted: Thu Dec 30, 2004 10:47 am 
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Joined: Thu Sep 04, 2003 8:23 am
Posts: 368
christian wrote:
It shouldn't make any difference for the query optimizer, even the driving table is easy to determine in both cases.


Sorry to say that but can you explain this a little bit : I don't take it.

Does hibernate generates theta or implicit join ? If hibernat generates theta, is it possible to know why it does that ?

Thanx

Seb


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