[jira] [Commented] (CALCITE-5771) Apply two different NULL semantics for CONCAT function(enabled in MySQL, Postgresql, BigQuery and MSSQL)

["Tanner Clary (Jira)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/CALCITE-5771?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17733664#comment-17733664 ] 

Tanner Clary commented on CALCITE-5771:
---------------------------------------

Closed in [3f2ae2f|https://github.com/apache/calcite/commit/3f2ae2f4dd2d6b1fab7c3a91e67a6a6d28523298], thanks for the PR [~VAE]!


> Apply two different NULL semantics for CONCAT function(enabled in MySQL, Postgresql, BigQuery and MSSQL)
> --------------------------------------------------------------------------------------------------------
>
>                 Key: CALCITE-5771
>                 URL: https://issues.apache.org/jira/browse/CALCITE-5771
>             Project: Calcite
>          Issue Type: Bug
>          Components: core
>    Affects Versions: 1.34.0
>            Reporter: ZheHu
>            Assignee: ZheHu
>            Priority: Major
>              Labels: pull-request-available
>
> We now have one CONCAT_FUNCTION which is enabled in MySQL, Postgresql, BigQuery, it always returns NULL when any of the arguments is NULL, and it accepts at least 2 arguments.
> The following table describes how different database products define CONCAT function:
> ||DB Product||Argument type in CONCAT||Argument num in CONCAT||Result||
> |MySQL|string|at least 1|returns null if any argument is null, otherwise return string|
> |BigQuery|string|at least 1|returns null if any argument is null, otherwise return string|
> |Postgresql|any(cast to string)|at least 1|always return string, null is treated as empty string|
> |MSSQL|string|2 ~ 254|always return string, null is treated as empty string|
> For MySQL and BigQuery, we can reuse the current CONCAT_FUNCTION(but need to change the accepted argument number). We also need another CONCAT function for Postgresql and MSSQL that treats NULL as empty String. And they both accept at least 1 argument.



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