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https://issues.apache.org/jira/browse/CALCITE-6678?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17899308#comment-17899308
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Julian Hyde commented on CALCITE-6678:
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You can't add tests in {{dummy.iq}}. That file is intentionally empty, for
debugging. Please move them somewhere else.
It would have been better to model {{DUAL}} as a view {{VALUES ('Y')}}. That
way it can be optimized, and doesn't force the plan to use enumerable
convention.
> Calcite should support dual table query when db provides this feature
> ---------------------------------------------------------------------
>
> Key: CALCITE-6678
> URL: https://issues.apache.org/jira/browse/CALCITE-6678
> Project: Calcite
> Issue Type: Improvement
> Reporter: Zhengqiang Duan
> Assignee: Zhengqiang Duan
> Priority: Major
> Labels: pull-request-available
> Fix For: 1.39.0
>
>
> Currently, both MySQL and Oracle support SQL like SELECT 1 + 1 FROM DUAL.
> When I tried to execute it in Calcite, the following exception occurred:
> {code:java}
> From line 1, column 19 to line 1, column 22: Object 'DUAL' not found {code}
> DUAL tables are commonly used in Oracle, and since Oracle requires that FROM
> be specified, I think we should support it.
> Here are some documents related to the DUAL table:
> * Oracle:
> [https://docs.oracle.com/en/database/oracle/oracle-database/23/sqlrf/Selecting-from-the-DUAL-Table.html]
> * MySQL: [https://dev.mysql.com/doc/refman/5.7/en/select.html]
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