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Object Relational Mapping
What are the joins in Hibernate ?
clojure forum advocate
Joined: Nov 08, 2003
Jan 20, 2006 06:05:00
The following lines are from Hibernate doc :
from eg.Cat as cat inner join cat.mate as mate left outer join cat.kittens as kitten from eg.Cat as cat left join cat.mate.kittens as kittens from Formula form full join form.parameter param select mate from eg.Cat as cat inner join cat.mate as mate
Would you mind telling me what do : inner join, left outer join, right outer join, full join mean ?
Thanks for help.
Joined: Sep 16, 2005
Jan 20, 2006 06:45:00
Joins are part of SQL/relational database theory and so are lifted directly into HQL, with some syntactic sugar. Here's a good article on them:
(Unforturnately, the forum software here is suspicious of those parens,
so copy and paste that into your browser's address bar...)
There is no emoticon for what I am feeling!
Joined: Apr 26, 2004
Jan 20, 2006 23:17:00
These are the basic join types in standard SQL. I would strongly suggest doing some basic SQL learning before using Hibernate as it will not entirely eliminate the need to know SQL.
Some people think they can use Hibernate as a means to entirely shield them from the relational data it is abstracting, this couldn't be any further from the truth.
It is sorta covered in the
JavaRanch Style Guide
subject: What are the joins in Hibernate ?
Regarding Hibernate Query
getting data from 2 tables using 2 DTOs
Recursive fetch join not recursively fetching all children
Sorry, but what does this select mean ?
left outer join *= how make compitible in HQL
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