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https://issues.apache.org/jira/browse/HIVE-16505?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16496252#comment-16496252
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Laszlo Bodor commented on HIVE-16505:
-------------------------------------
[~kgyrtkirk] : 01.patch attached. Could you please check if the introduced
qtest covers all the relevant cases?
> Support "unknown" boolean truth value
> -------------------------------------
>
> Key: HIVE-16505
> URL: https://issues.apache.org/jira/browse/HIVE-16505
> Project: Hive
> Issue Type: Sub-task
> Components: SQL
> Reporter: Zoltan Haindrich
> Assignee: Laszlo Bodor
> Priority: Major
> Attachments: HIVE-16505.01.patch
>
>
> according to the standard, boolean truth value might be:
> {{TRUE|FALSE|UNKNOWN}}.
> similar queries to the following should be supported:
> {code:java}
> select 1 where null is unknown;
> select 1 where (select cast(null as boolean) ) is unknown;
> {code}
> "unknown" behaves similarily to null. {{(null=null) is null}}
>
> "All boolean values and SQL truth values are comparable and all are
> assignable to a site of type boolean. The value True is greater than the
> value False, and any comparison involving the null value or an Unknown truth
> value will return an Unknown result. The values True and False may be
> assigned to any site having a boolean data type; assignment of Unknown, or
> the null value, is subject to the nullability characteristic of the target."
>
> *Truth table for the AND boolean operator*
> AND True False Unknown
> True True False Unknown
> False False False False
> Unknown Unknown False Unknown
> *Truth table for the OR boolean operator*
> OR True False Unknown
> True True True True
> False True False Unknown
> Unknown True Unknown Unknown
> *Truth table for the IS boolean operator*
> IS TRUE FALSE UNKNOWN
> True True False False
> False False True False
> Unknown False False True
>
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