Difference between revisions of "EclipseLink/UserGuide/JPA/Basic JPA Development/Querying/Batch Reading"

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(New page: {{EclipseLink_UserGuide |info=y |toc=n |eclipselink=y |eclipselinktype=JPA}} = Batch Reading Using exist and IN = Doc in process 02/24/11 <!-- ({{bug|298985}}) Typically batch readi...)
 
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= Batch Reading Using exist and IN =
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= Batch Reading Using EXIST and IN =
  
 
Doc in process 02/24/11
 
Doc in process 02/24/11
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<!--
 
<!--
 
({{bug|298985}})
 
  
 
Typically batch reading uses a join of the batch query to the source query.
 
Typically batch reading uses a join of the batch query to the source query.
  
 
This join has some issues:
 
This join has some issues:
* If a m-1 or m-m, join causes duplicate rows to be selected, (a distinct is used to filter rows for m-1, but duplicates are returned for m-m as join table info is needed).
+
* If a many-to-one or a many-to-many, using join causes duplicate rows to be selected. (A DISTINCT clause is used to filter rows for many-to-one, but duplicates are returned for many-to-many, because join table information is needed).
 
* DISTINCT does not work with LOBs.
 
* DISTINCT does not work with LOBs.
 
* DISTINCT may be less efficient on some databases than alternatives.
 
* DISTINCT may be less efficient on some databases than alternatives.

Revision as of 13:27, 24 February 2011

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Batch Reading Using EXIST and IN

Doc in process 02/24/11


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