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https://issues.apache.org/jira/browse/HIVE-12082?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15370323#comment-15370323
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Lefty Leverenz commented on HIVE-12082:
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I'm not sure either, but the doc should mention 1.3.0 so I'll add a TODOC1.3
label to HIVE-14189. Here's the doc link:
* [Mathematical Functions (greatest & least are at end of table) |
https://cwiki.apache.org/confluence/display/Hive/LanguageManual+UDF#LanguageManualUDF-MathematicalFunctions]
> Null comparison for greatest and least operator
> -----------------------------------------------
>
> Key: HIVE-12082
> URL: https://issues.apache.org/jira/browse/HIVE-12082
> Project: Hive
> Issue Type: Bug
> Components: UDF
> Reporter: Szehon Ho
> Assignee: Szehon Ho
> Fix For: 2.0.0
>
> Attachments: HIVE-12082.2.patch, HIVE-12082.patch
>
>
> In mysql comparisons if any of the entries are null, then the result is null.
> [https://dev.mysql.com/doc/refman/5.0/en/comparison-operators.html|https://dev.mysql.com/doc/refman/5.0/en/comparison-operators.html]
> and
> [https://dev.mysql.com/doc/refman/5.0/en/type-conversion.html|https://dev.mysql.com/doc/refman/5.0/en/type-conversion.html].
> This can be demonstrated by the following mysql query:
> {noformat}
> mysql> select greatest(1, null) from test;
> +-------------------+
> | greatest(1, null) |
> +-------------------+
> | NULL |
> +-------------------+
> 1 row in set (0.00 sec)
> mysql> select greatest(-1, null) from test;
> +--------------------+
> | greatest(-1, null) |
> +--------------------+
> | NULL |
> +--------------------+
> 1 row in set (0.00 sec)
> {noformat}
> This is in contrast to Hive, where null are ignored in the comparisons.
> {noformat}
> hive> select greatest(null, 1) from test;
> OK
> 1
> {noformat}
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