[jira] [Commented] (KYLIN-4041) CONCAT NULL not working properly

["ASF GitHub Bot (JIRA)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/KYLIN-4041?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16861824#comment-16861824 ] 

ASF GitHub Bot commented on KYLIN-4041:
---------------------------------------

vaful commented on pull request #684: KYLIN-4041 CONCAT NULL not working properly
URL: https://github.com/apache/kylin/pull/684
 
 
   
 
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> CONCAT NULL not working properly
> --------------------------------
>
>                 Key: KYLIN-4041
>                 URL: https://issues.apache.org/jira/browse/KYLIN-4041
>             Project: Kylin
>          Issue Type: Improvement
>            Reporter: Yifei Wu
>            Assignee: Yifei Wu
>            Priority: Major
>
> to support SQL 'concat' function, Kylin introduces a UDF named ConcatUDF.
> but the NULL case cannot deal with correctly, like the below sql:
> ```
> select
>  concat(meta_categ_name, CAST(null as VARCHAR)) as c1, 
>  concat(meta_categ_name, ' Catagory') as c2
>  from test_kylin_fact
>  left JOIN edw.test_cal_dt as test_cal_dt
>  ON test_kylin_fact.cal_dt = test_cal_dt.cal_dt
>  left JOIN test_category_groupings
>  ON test_kylin_fact.leaf_categ_id = test_category_groupings.leaf_categ_id AND test_kylin_fact.lstg_site_id = test_category_groupings.site_id
>  left JOIN edw.test_sites as test_sites
>  ON test_kylin_fact.lstg_site_id = test_sites.site_id
>  where meta_categ_name = 'Computers'
>  group by meta_categ_name
>  order by meta_categ_name
>  limit 1
> ```
> when CONCAT value with NULL, the result is expected to be still NULL.



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