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From "Maryann Xue (JIRA)" <j...@apache.org>
Subject [jira] [Updated] (PHOENIX-167) Support semi/anti-joins
Date Thu, 14 Aug 2014 03:06:13 GMT

     [ https://issues.apache.org/jira/browse/PHOENIX-167?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
]

Maryann Xue updated PHOENIX-167:
--------------------------------

    Issue Type: Sub-task  (was: Task)
        Parent: PHOENIX-1167

> Support semi/anti-joins
> -----------------------
>
>                 Key: PHOENIX-167
>                 URL: https://issues.apache.org/jira/browse/PHOENIX-167
>             Project: Phoenix
>          Issue Type: Sub-task
>            Reporter: James Taylor
>            Assignee: Maryann Xue
>              Labels: enhancement
>
> A semi-join between two tables returns rows from the first table where one or more matches
are found in the second table. The difference between a semi-join and a conventional join
is that rows in the first table will be returned at most once. Even if the second table contains
two matches for a row in the first table, only one copy of the row will be returned. Semi-joins
are written using the EXISTS or IN constructs.
> An anti-join is the opposite of a semi-join and is written using the NOT EXISTS or NOT
IN constructs.
> There's a pretty good write-up [here] (http://www.dbspecialists.com/files/presentations/semijoins.html)
on semi/anti joins.



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