Szehon Ho created HIVE-12082:
--------------------------------
Summary: Null comparison for greatest and least operator
Key: HIVE-12082
URL: https://issues.apache.org/jira/browse/HIVE-12082
Project: Hive
Issue Type: Bug
Reporter: Szehon Ho
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 does not win in greatest, least over
values.
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