[
https://issues.apache.org/jira/browse/JDO-721?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14175206#comment-14175206
]
Craig L Russell commented on JDO-721:
-------------------------------------
followed by one of the following words: “ascending”, “descending”,“asc”, or
“desc”, followed by an optional null position specification.
...
The optional null position specification consists of either nulls first or
nulls last. If nulls first is specified, instances containing null-valued
fields are orderd before instances whose fields contain non-null values. If
nulls last is specified, instances containing null-valued fields are orderd
after instances whose fields contain non-null values. Without a null position
the ordering of null values is not specified.
suggest:
followed by one of the following words: “ascending”, “descending”,“asc”, or
“desc”, followed by an optional null position specification "nulls first" or
"nulls last".
...
The optional null position specification consists of either "nulls first" or
"nulls last". If "nulls first" is specified, instances containing null-valued
fields are ordered before instances whose fields contain non-null values. If
"nulls last" is specified, instances containing null-valued fields are ordered
after instances whose fields contain non-null values. Without a null position
the ordering of null values is not specified.
> Specifying NULL elements positioning in ordered columns
> -------------------------------------------------------
>
> Key: JDO-721
> URL: https://issues.apache.org/jira/browse/JDO-721
> Project: JDO
> Issue Type: Improvement
> Components: specification
> Affects Versions: JDO 3 update 1 (3.0.1)
> Reporter: Muhammad Gelbana
> Assignee: Michael Bouschen
> Priority: Minor
> Labels: jdoql
> Fix For: JDO 3.1
>
> Attachments: JDO-721.patch
>
>
> I don't know about other RDBMS but in MySQL ordering, it's possible to
> specify whether NULL column fields are placed in the beginning or at the end
> of the ordering, i.e.:
> ORDER BY `values_column` IS NULL DESC
> [values_column]
> NULL
> NULL
> value1
> value2
> value3
> or the other way around (ORDER BY `values_column` IS NULL ASC):
> [values_column]
> value1
> value2
> value3
> NULL
> NULL
> I checked JDO 3 specification and found that JDOQL's ordering specification
> doesn't support specifying NULL values handling:
> ------------------------------------------------------------------------------
> 26.7 Ordering Specification
> This section describes the syntax of the setOrdering argument.
> OrderingClause:
> OrderingSpecs ,opt
> OrderingSpecs:
> OrderingSpec
> OrderingSpecs , OrderingSpec
> OrderingSpec:
> Expression Ascending
> Expression Descending
> Ascending: one of
> asc ascending
> Descending: one of
> desc descending
> Please note, as a usability feature OrderingClause supports an optional
> trailing comma.
> ------------------------------------------------------------------------------
> Thank you for your time and efforts.
--
This message was sent by Atlassian JIRA
(v6.3.4#6332)
