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https://issues.apache.org/jira/browse/CALCITE-7613?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=18090383#comment-18090383
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Julian Hyde commented on CALCITE-7613:
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Calcite already has a CONCAT function. SqlLibraryOperators.CONCAT_FUNCTION. Why
did you not mention this?
Can you be clear whether you are talking about SQL-level changes or internal
changes? It's impossible to write SQL that gives '||", an infix operator, more
than two arguments.
> Support multi-operand CONCAT operator
> -------------------------------------
>
> Key: CALCITE-7613
> URL: https://issues.apache.org/jira/browse/CALCITE-7613
> Project: Calcite
> Issue Type: Improvement
> Components: core
> Affects Versions: 1.42.0
> Reporter: Yu Xu
> Assignee: Yu Xu
> Priority: Minor
> Labels: pull-request-available
> Fix For: 1.43.0
>
>
> Currently, Calcite's CONCAT operator (the || string concatenation operator)
> is defined as a SqlBinaryOperator, which restricts it to exactly two operands
> at the RexNode level.
> This limitation forces users to manually construct nested CONCAT calls or use
> workarounds when dealing with multiple string concatenations.
> When attempting to concatenate more than two strings:
> {code:java}
> -- Desired SQL (currently fails at RexNode construction)
> SELECT CONCAT('Hello', ' ', 'World', '!');
> -- Or using the || operator
> SELECT 'Hello' || ' ' || 'World' || '!'; {code}
> If you try to construct 3+ operands it would error out:
> {code:java}
> wrong operand count 3 for ||
> {code}
> Mainstream databases today, such as PostgreSQL and Oracle, support
> multi-argument `CONCAT`.
> postgresql：[https://onecompiler.com/postgresql/44sufvv78]
> oracle：https://onecompiler.com/plsql/44sufwevp
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