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https://issues.apache.org/jira/browse/CALCITE-5745?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17728933#comment-17728933
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Julian Hyde commented on CALCITE-5745:
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Thanks for doing the research on Oracle. I agree with you that CONCAT is the
exception rather than the rule in Oracle and we should implement a CONCAT2
function in Calcite that has the same null semantics.
I think we need one CONCAT function that ignores NULL arguments (treats them as
empty strings) and one that returns NULL if any arguments are NULL. I think
both functions should accept a variable number of arguments (at least one).
Do you agree that two functions are sufficient?
> CONCAT2 function(enabled in Oracle library) gets wrong result when one of the
> argument is NULL
> ----------------------------------------------------------------------------------------------
>
> Key: CALCITE-5745
> URL: https://issues.apache.org/jira/browse/CALCITE-5745
> Project: Calcite
> Issue Type: Bug
> Components: core
> Affects Versions: 1.34.0
> Reporter: ZheHu
> Assignee: ZheHu
> Priority: Major
>
> Tested CONCAT function in Oracle and got the corresponding results.
> {code}
> select concat('a', cast(null as varchar(20))) from DUAL;
> --- results in 'a'
> {code}
> {code}
> select concat('a', null) from DUAL;
> select 'a' || null from DUAL;
> --- both result in 'a'
> {code}
> In Calcite(see checkConcat2Func() in SqlOperatorTest.java), CONCAT2 function
> gets null when running:
> {code}
> concat('a', cast(null as varchar))
> {code}
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