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https://issues.apache.org/jira/browse/FLINK-9559?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16591533#comment-16591533
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ASF GitHub Bot commented on FLINK-9559:
---------------------------------------
hequn8128 edited a comment 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-415735866
Hi @pnowojski , thanks for your reply. There are many cases need this
feature. Not only `case when`, but also `nvl`, `greatest` and `least`. Most
users encounter the blank problem is `case when`. Examples have been added in
the test cases. Below I will add some more examples:
1.
```
SELECT country_name
FROM (
SELECT CASE id
WHEN 1 THEN 'GERMANY'
WHEN 2 THEN 'CANADA'
ELSE 'INVALID COUNTRY ID'
END AS country_name
FROM country_id
)
WHERE country_name = 'GERMANY'
```
This sql will output nothing since the blank problem. It is very confused.
2.
```
SELECT country_name, country_info
FROM (
SELECT CASE id
WHEN 1 THEN 'GERMANY'
WHEN 2 THEN 'CANADA'
ELSE 'INVALID COUNTRY ID'
END AS country_name
FROM country_id
) nameTable join infoTable on nameTable.country_name =
infoTable.country_name;
```
This sql cannot join correctly since the blank problem. 'GERMANY' in
nameTable becomes 'GERMANY-----------'. BTW, '-' means the blank.
It is true the sql standard returns CHAR type, but nearly all major DBMSs
return VARCHAR without blank-padded.
Thanks, Hequn
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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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