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https://issues.apache.org/jira/browse/CALCITE-6430?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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xiong duan updated CALCITE-6430:
--------------------------------
    Summary: SINGLE_VALUE rewrite to wrong sql when the sub-query return one 
NOT-NULL value and NULL value in PostgreSQL、MySQL、HSQL dialect  (was: 
SINGLE_VALUE rewrite to wrong sql when the sub-query return one not-null value 
and NULL value in PostgreSQL、MySQL、HSQL dialect)

> SINGLE_VALUE rewrite to wrong sql when the sub-query return one NOT-NULL 
> value and NULL value in PostgreSQL、MySQL、HSQL dialect
> ------------------------------------------------------------------------------------------------------------------------------
>
>                 Key: CALCITE-6430
>                 URL: https://issues.apache.org/jira/browse/CALCITE-6430
>             Project: Calcite
>          Issue Type: Improvement
>          Components: core
>    Affects Versions: 1.37.0
>            Reporter: xiong duan
>            Assignee: xiong duan
>            Priority: Major
>             Fix For: 1.38.0
>
>
> Calcite rewrite the SINGLE_VALUE to different sql :
> For example in HSQL:
> {code:java}
> CASE COUNT(*)
> WHEN 0 THEN NULL
> WHEN 1 THEN MIN(<result>)
> ELSE (VALUES 1 UNION ALL VALUES 1)
> END{code}
> This is right. But Calcite will generate:
> {code:java}
> CASE COUNT(result) 
> WHEN 0 THEN NULL
> WHEN 1 THEN MIN(<result>)
> ELSE (VALUES 1 UNION ALL VALUES 1)
> END{code}
> This sql will return wrong result.
> For Example:
> tableA:
> ||c1||c2||
> |4|1|
> |NULL|NULL|
> |NULL|NULL|
> |NULL|NULL|
> TheSQL:
> {code:java}
> select *
> from tableA
> where c1 > (select c2 from tableA);{code}
> will throw : [21000][1242] Subquery returns more than 1 row
> But SQL:
> {code:java}
> select *
> from tableA left join (select case count(c2)
> when 0 then null
> when 1 then min(c2)
> else (select cast(null as integer) union all select cast(null as integer)) 
> end as alias
> from tableA) as t1 on true
> where tableA.c1 > t1.alias;{code}
> will return one row value.



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