[jira] [Updated] (CALCITE-5741) Add support for CONCAT_WS function (enabled in MSSQL, MySQL and Postgres)

["Julian Hyde (Jira)" <ji...@apache.org>]

     [ https://issues.apache.org/jira/browse/CALCITE-5741?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]

Julian Hyde updated CALCITE-5741:
---------------------------------
    Summary: Add support for CONCAT_WS function (enabled in MSSQL, MySQL and Postgres)  (was: Add support for CONCAT_WS function(enabled in MSSQL, MySQL and Postgresql))

> Add support for CONCAT_WS function (enabled in MSSQL, MySQL and Postgres)
> -------------------------------------------------------------------------
>
>                 Key: CALCITE-5741
>                 URL: https://issues.apache.org/jira/browse/CALCITE-5741
>             Project: Calcite
>          Issue Type: Improvement
>          Components: core
>    Affects Versions: 1.34.0
>            Reporter: ZheHu
>            Assignee: ZheHu
>            Priority: Minor
>              Labels: pull-request-available
>
> This function returns a string resulting from the concatenation, or joining, of two or more string values in an end-to-end manner. It separates those concatenated string values with the delimiter specified in the first function argument. It has the following syntax:
> {code:java}
> CONCAT_WS ( separator, argument1, argument2 [, argumentN]... )
> {code}
> Unlike CONCAT function, CONCAT_WS ignores NULL value, for example:
> {code:java}
> select concat_ws(',', 'a', 'b', null, null, 'c');
> -- result in 'a,b,c'
> {code}
> One important thing to be noted is that CONCAT_WS has two *NULL semantics for the separator argument* in different Database products(So we need two function in Calcite to represent).
> Taking the following SQL as an example:
> {code:java}
> select concat_ws(null, 'a', 'b', null, null, 'c');
> {code}
>  - {*}MSSQL{*}: never returns null and treats null as empty string, so the above SQL results in "abc" (For more details, see [mssql-concat_ws|https://learn.microsoft.com/en-us/sql/t-sql/functions/concat-ws-transact-sql?view=sql-server-ver16])
>  - {*}MySQL and Postgresql{*}: returns null when the separator is null, so the example SQL returns NULL.



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