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https://issues.apache.org/jira/browse/HIVE-832?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12755613#action_12755613
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Namit Jain commented on HIVE-832:
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Yes, but there was a usecase when this was being used to do perform subtraction
(A - B).
> Disallow OUTER JOIN with partition in WHERE clause in strict mode
> -----------------------------------------------------------------
>
> Key: HIVE-832
> URL: https://issues.apache.org/jira/browse/HIVE-832
> Project: Hadoop Hive
> Issue Type: Wish
> Reporter: Adam Kramer
>
> There is a wide-range poorly-understood issue in how WHERE and ON clauses
> work in the case of outer joins.
> The WHERE filter is applied after the join. After an outer join, the INNER
> table (the left table in a RIGHT OUTER, or the left table in the LEFT OUTER)
> has all columns set to NULL for all rows. As a result, if ANY of them are
> cited in the WHERE clause, they will equal NULL. This almost always causes
> the join to effectively be an INNER join, even though the user typed the word
> O-U-T-E-R, probably for good reason.
> In strict mode, we should not allow ANY COLUMNS from the inner table to
> appear in the WHERE clause.
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