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From "Jeff Levitt (JIRA)" <derby-...@db.apache.org>
Subject [jira] Commented: (DERBY-402) INTERSECT/EXCEPT/UNION operators don't agree with documented behavior.
Date Fri, 17 Feb 2006 20:14:25 GMT
    [ http://issues.apache.org/jira/browse/DERBY-402?page=comments#action_12366845 ] 

Jeff Levitt commented on DERBY-402:
-----------------------------------

So I'm trying to understand the doc impact of this bug.  Should the offending sentences just
be removed?

Thanks!

> INTERSECT/EXCEPT/UNION operators don't agree with documented behavior.
> ----------------------------------------------------------------------
>
>          Key: DERBY-402
>          URL: http://issues.apache.org/jira/browse/DERBY-402
>      Project: Derby
>         Type: Bug
>   Components: Documentation
>     Versions: 10.1.1.0, 10.0.2.2
>     Reporter: A B
>      Fix For: 10.2.0.0

>
> I noticed the following two differences between what the documentation (Reference Manual)
says about UNION/INTERSECT/EXCEPT queries and what the actual Derby behavior is.  I'm filing
this issue as a single "bug" against Derby, but if it turns out later that this is really
just a documentation issue, or that these are "improvements" instead of bugs, anyone should
feel free to change the relevant fields in this issue...
> 1) -- p. 63 of the Reference Manual (PDF version): "SelectExpression" -> "Naming columns"
> First paragraph in this section includes the following:
>     When the SelectExpression appears in a UNION, INTERSECT,
>     or EXCEPT operator, the names from the first SelectExpression
>     are taken as the names for the columns in the result of
>     the operation.
> But this doesn't appear to be true.  Ex:
> ij> select a from t1 union select b from t2;
> 1				// This "1" should be "A", according to doc.
> -----------
> 1
> 2
> If this behavior is intentional, then an ORDER BY clause on a UNION/INTERSECT/EXCEPT
result set can only reference the result columns by position (ex. would have to use "order
by 1" in the above query since "order by  a" doesn't work (because the name of the result
column isn't "a")).
> Note that if both SelectExpressions have the same column name, then things work  differently:
> ij> select a from t1 union select b as a from t2;
> A				// Now it's "A" instead of "1".
> -----------
> 1
> 2
> So what needs to be corrected here?  The documentation or the code?
> 2) -- p. 133 of  the Reference Manual: "Dynamic Parameters" ->  "Where dynamic parameters
are allowed"
> Number 16 says "a dynamic parameter is allowed to represent a column if it appears in
a UNION, INTERSECT, or EXCEPT expression."  But the two examples that it gives both fail:
> ij> SELECT ? FROM t UNION SELECT 1 FROM t;
> ERROR 42X34: There is a ? parameter in the select list.  This is not allowed.
> ij> VALUES 1 UNION VALUES ?;
> ERROR 42X34: There is a ? parameter in the select list.  This is not allowed.
> I also tried preparing these statements using JDBC, but they failed there with the same
error..

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