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why  fetch join in hibernate

Posted on 2009-05-11
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Last Modified: 2013-11-24
please see this hibernate tutorial. i have question here

http://72.14.235.132/search?q=cache:Va2qJokS5gwJ:www.metaarchit.com/hibernate_tutorials/Hibernate%2520Tutorial%252004.pdf+Hibernate+Association&cd=9&hl=en&ct=clnk&gl=in&client=firefox-a


see this code given in that tutorial  under   "1.2 Fetching strategies"

<hibernate-mapping package="com.metaarchit.bookshop">
<class name="Book" table="BOOK">
...
<many-to-one name="publisher" class="Publisher" column="PUBLISHER_ID"
lazy="false" fetch="join" />
</class>
</hibernate-mapping>


My Question is , why do we use fetch="join"  in the above ?  if we just  have lazy="false"  then book and chapters both will be loaded .....so why  extra fetch="join"  again ?   i think we can skip fetch="join"  .....i am not clear at this part.
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Question by:cofactor
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you would do that to avoid the second select, and select the related publisher using a join


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by:cofactor
ID: 24360809
Ahh...so   this is just a performance issue here ...earlier two select query fired ...now single select query will be fired because of this "join"  thingie  ...good to know ...thanks


thanks


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