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https://issues.apache.org/jira/browse/JDO-637?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12736129#action_12736129
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Craig Russell commented on JDO-637:
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+1 to what Andy says.
Simple cases don't even need any special syntax. The first example can be
written as SELECT this.x, this,y, this.b.z FROM package.A where this.b != null.
Additionally, JDOQL already has the capability of joining persistent classes,
using the variable syntax described in 14.6.5. The variables allow joining
based on persistent fields that describe the relationships.
Inner versus outer joins are distinguished based on whether the reference is
null or not. The default for JDOQL is "outer join" semantics. If you want
"inner join" semantics, disallow null values. For example, you can join
Employee and Department even if an Employee has no Department, but you can
restrict Employees to those with Department references by using e.dept != null
in the query.
> JDOQL : Enhance the JDOQL with JOIN and ALIAS features
> -------------------------------------------------------
>
> Key: JDO-637
> URL: https://issues.apache.org/jira/browse/JDO-637
> Project: JDO
> Issue Type: New Feature
> Components: api2
> Reporter: Eric SULTAN
>
> JOIN examples :
> SELECT this.x, this,y, this.b.z FROM package.A JOIN this.b
> SELECT this.x, this,y, this.b.z FROM package.A LEFT OUTER JOIN this.b
> ALIAS examples :
> SELECT alias1.x, alias1.y, alias1.b.z FROM package.A alias1 WHERE
> alias1.number > 10
> JOIN and ALIAS examples :
> SELECT alias1.x, alias1.y, alias1.b.z FROM package.A alias1 LEFT OUTER JOIN
> alias1.b WHERE alias1.number > 10
> SELECT alias1.x, alias1.y, alias2.z FROM package.A alias1 LEFT OUTER JOIN
> alias1.b alias2 WHERE alias1.number > 10
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