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https://issues.apache.org/jira/browse/CALCITE-1892?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16091574#comment-16091574
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Kevin Hinterlong commented on CALCITE-1892:
-------------------------------------------

I think that would work for most cases. The only one I know which wouldn't work 
is SQLite which needs something like (taken from one of the answers in the 
Stack Overflow post, I don't use or need it).

{code:sql}
    SELECT * FROM (SELECT *
    FROM "PUBLIC"."TEST"
    ORDER BY "TEST_VALUE"
    LIMIT 1
    OFFSET 0)
    UNION ALL
    SELECT * FROM (SELECT *
    FROM "PUBLIC"."TEST"
    ORDER BY "TEST_VALUE"
    LIMIT 2
    OFFSET 1)
{code}

> Relbuilder .union(...) should use parentheses after .sortLimit(...) is called
> -----------------------------------------------------------------------------
>
>                 Key: CALCITE-1892
>                 URL: https://issues.apache.org/jira/browse/CALCITE-1892
>             Project: Calcite
>          Issue Type: Bug
>          Components: jdbc-adapter
>    Affects Versions: 1.13.0
>         Environment: Java 7
> H2 version 1.4.195
> Calcite version 1.13.0
>            Reporter: Kevin Hinterlong
>            Assignee: Julian Hyde
>              Labels: newbie
>
> I'm trying to build up multiple queries separately as {{RelNode}} , then call
> {{builder.pushAll(unionParts).union(true);}}
> to union the results in SQL, but I end up with
> {{org.h2.jdbc.JdbcSQLException: Syntax error in SQL statement}}
> It turns out to be an issue with lack of parentheses between calls to {{UNION 
> ALL}}
> I've done some digging and according to [the mysql 
> docs|https://dev.mysql.com/doc/refman/5.7/en/union.html] the union call needs 
> to have these RelNode's (or their equivalent sql) wrapped in parentheses when 
> using {{ORDER BY}} and {{LIMIT}} which is
> {{.sortLimit(offset, fetch, builder.field("TEST_VALUE"))}}
> with the {{RelBuilder}}
> I've been able to resolve this by converting each {{RelNode}} to SQL and 
> manually wrapping it in parentheses between calls to {{UNION ALL}} before 
> executing the statement against H2 
> Like so: (<insert query>) UNION ALL (<insert query>) 
> Here's an example I made to show exactly what's happening 
> [kevinhinterlong/CalciteUnionError|https://github.com/kevinhinterlong/CalciteUnionError]



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