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https://issues.apache.org/jira/browse/KYLIN-5279?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17622601#comment-17622601
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liyang commented on KYLIN-5279:
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NULL is smaller or larger? It depends.
The answe depends on the SQL vendor. Below is a summary from
[https://learnsql.com/blog/how-to-order-rows-with-nulls/]
* PostgreSQL / Oracle — NULL is larger, by default
* MySQL / SQL Server — NULL is smaller, by default
Of course, the default behavior is configurable in most of these products.
The PR looks good as it lets KYLIN behavior configurable as well. 👍
> Default null collation for Kylin5.0 sqls should be null-last for ASC order
> and null-first for DESC order.
> ---------------------------------------------------------------------------------------------------------
>
> Key: KYLIN-5279
> URL: https://issues.apache.org/jira/browse/KYLIN-5279
> Project: Kylin
> Issue Type: Bug
> Components: Query Engine
> Reporter: Zhenning Zhang
> Assignee: Zhenning Zhang
> Priority: Major
> Fix For: 5.0-alpha
>
> Attachments: image-2022-10-20-15-12-12-967.png
>
>
> according to pgsql:
> [https://www.postgresql.org/docs/current/queries-order.html]
> "By default, null values sort as if larger than any non-null value; that is,
> {{NULLS FIRST}} is the default for {{DESC}} order, and {{NULLS LAST}}
> otherwise."
> currently, the result is:
> !image-2022-10-20-15-12-12-967.png|width=1320,height=743!
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