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From "Ted Xu (JIRA)" <j...@apache.org>
Subject [jira] Commented: (HIVE-741) NULL is not handled correctly in join
Date Fri, 13 Aug 2010 11:36:21 GMT

    [ https://issues.apache.org/jira/browse/HIVE-741?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12898194#action_12898194
] 

Ted Xu commented on HIVE-741:
-----------------------------

Sorry I'm mistakenly expressed my idea, I mean values with NULL join keys shall be filtered
out in mappers. 

I think values with NULL join keys shall be filtered out because NULL equals nothing, and
Hive only support equal join.

Please correct me if I'm wrong. 

> NULL is not handled correctly in join
> -------------------------------------
>
>                 Key: HIVE-741
>                 URL: https://issues.apache.org/jira/browse/HIVE-741
>             Project: Hadoop Hive
>          Issue Type: Bug
>            Reporter: Ning Zhang
>            Assignee: Amareshwari Sriramadasu
>
> With the following data in table input4_cb:
> Key        Value
> ------       --------
> NULL     325
> 18          NULL
> The following query:
> {code}
> select * from input4_cb a join input4_cb b on a.key = b.value;
> {code}
> returns the following result:
> NULL    325    18   NULL
> The correct result should be empty set.
> When 'null' is replaced by '' it works.

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