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https://issues.apache.org/jira/browse/FLINK-9559?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16590333#comment-16590333
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ASF GitHub Bot commented on FLINK-9559:
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pnowojski commented on issue #6519: [FLINK-9559] [table] The type of a union of 
CHAR columns of different lengths should be VARCHAR
URL: https://github.com/apache/flink/pull/6519#issuecomment-415443589
 
 
   At least according to draft of 2008 SQL Standard, this PR violates it 
(paragraph 9.3, section 3) iii) 3) says that the result type in this case 
should be `CHAR(N)` where N is the maximum of the inputs. If any of the inputs 
is `VARCHAR(x)`, the result should be also `VARCHAR`.

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> The type of a union of CHAR columns of different lengths should be VARCHAR
> --------------------------------------------------------------------------
>
>                 Key: FLINK-9559
>                 URL: https://issues.apache.org/jira/browse/FLINK-9559
>             Project: Flink
>          Issue Type: Bug
>          Components: Table API & SQL
>            Reporter: Hequn Cheng
>            Assignee: Hequn Cheng
>            Priority: Major
>              Labels: pull-request-available
>
> Currently, If the case-when expression has two branches which return string 
> literal, redundant white spaces will be appended to the short string literal. 
> For example, for the sql: case 1 when 1 then 'a' when 2 then 'bcd' end, the 
> return value will be 'a ' of CHAR(3) instead of 'a'.
> Although, this follows the behavior in strict SQL standard mode(SQL:2003). We 
> should get the pragmatic return type in a real scenario without blank-padded. 
> Happily, this problem has been fixed by 
> [CALCITE-2321|https://issues.apache.org/jira/browse/CALCITE-2321], we can 
> upgrade calcite to the next release(1.17.0) and override 
> {{RelDataTypeSystem}} in flink to configure the return type, i.e., making 
> {{shouldConvertRaggedUnionTypesToVarying()}} return true.



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