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Date: Sat, 08 Nov 2003 18:25:51 +0100
From: Jakob Braeuchi <jbraeuchi@gmx.ch>
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To: OJB Developers List <ojb-dev@db.apache.org>
Subject: Re: Columns listed multiple times in select clause
References: <3FAC2AE9.80009@x2dev.com>
In-Reply-To: <3FAC2AE9.80009@x2dev.com>
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hi matt,

i can not reproduce the behaviour you mentioned in your post.
ensureColumns expects a list of attributeNames _not_ dbColumns.

please post your query and the resulting sql.

jakob

Matt Mastrangelo wrote:
> Hello,
> 
> I'm having a problem with a SQL statement returned by a call to 
> org.apache.ojb.broker.accesslayer.sql.SqlGeneratorDefaultImpl#getPreparedSelectStatement(...).  
> The SELECT statement returned lists all the columns referenced in the 
> ORDER BY clause twice in the SELECT clause.
> 
> Here is what appears to be the causing the problem:
> 
> In 
> org.apache.ojb.broker.accesslayer.sql.SqlSelectStatement#getStatement(), 
> ensureColumns is called if the query contains an ORDER BY or GROUP BY 
> clause.  The ensureColumns method attempts to make sure that any fields 
> referenced in an ORDER BY or GROUP BY are included in the SELECT 
> clause.  A list of class attribute names retrieved by a call to 
> appendListOfColumnsForSelect is passed to ensureColumns.
> 
> The problem seems to be that ensureColumns is expecting a list of 
> database column names, not class attribute names.  It checks the list to 
> see if the field in the ORDER BY/GROUP BY exists, and if not, it adds it 
> to the SELECT clause.  But because the list contains attribute names and 
> not database column names, none of the fields are found in the passed 
> list. Hence, all fields in ORDER BY/GROUP BY clauses are being appended 
> to the SELECT clause, even if they are already present.
> 
> This causes problems in some databases, such as Microsoft SQL Server, 
> where the same field cannot be present more than once in the SELECT 
> clause.  This doesn't cause a problem in other databases, such as 
> Interbase/Firebird, that allow columns to appear multiple times.
> 
> Has this problem been reported before, and if so, are there any known 
> workarounds?
> Thanks for your help.
> 
> Matt Mastrangelo
> 
> 
> 
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