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From "Rick Curtis (JIRA)" <j...@apache.org>
Subject [jira] Commented: (OPENJPA-1794) Result of aggregate function MAX is 0 on empty table (instead of NULL).
Date Wed, 15 Sep 2010 13:50:32 GMT

    [ https://issues.apache.org/jira/browse/OPENJPA-1794?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12909731#action_12909731
] 

Rick Curtis commented on OPENJPA-1794:
--------------------------------------

Per the spec : 
> If SUM, AVG, MAX, or MIN is used, and there are no values to which the aggregate function
can be applied, the result of the aggregate function is NULL.

Something else to muddy the waters....
> The Java type that is contained in the result of a query using an aggregate function
is as follows:
> ...
> *MAX, MIN return the type of the state field to which they are applied.

In the example detailed above, lets say the p.pk field is a primitive long... A NULL primitive
is zero so in that case, it would appear that we are working properly. If p.pk is a java.lang.Long,
we are not.

> Result of aggregate function MAX is 0 on empty table (instead of NULL).
> -----------------------------------------------------------------------
>
>                 Key: OPENJPA-1794
>                 URL: https://issues.apache.org/jira/browse/OPENJPA-1794
>             Project: OpenJPA
>          Issue Type: Bug
>          Components: query
>    Affects Versions: 2.0.0
>            Reporter: Vera Filippova
>
> Below is a snippet of a test case... the max should be null, but is zero.
>             Object count = em.createQuery("Select count(p.pk) from Entity1 p where 1=1").getSingleResult();
>             Object max = em.createQuery("Select max(p.pk) from Entity1 p where 1=1").getSingleResult();
>             System.out.println("count:"+count+ " max:"+max);
>             > count:0 max:0

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