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Difference between revisions of "EclipseLink/UserGuide/JPA/Basic JPA Development/Querying/Batch Reading"
< EclipseLink | UserGuide | JPA | Basic JPA Development | Querying
(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 | + | = Batch Reading Using EXIST and IN = |
Doc in process 02/24/11 | Doc in process 02/24/11 | ||
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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 | + | * 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
