David,
I need create aliases when a table is used more then once in a EJB-QL query.
It is really easy to get into this situation, so aliases are always used. I
could let the db compain, but then the user would have no recourse, as
EJB-QL is currently the only way to define an ejbSelect. I looked at the
getSQLKeywords function, and I think it is a good start. We will still need
the ability to specify additional keywords, because the drivers sometimes
lie.
Does this explain the issue more? This is only for EJB-QL, but could be
expanded to other auto-generation code like table and column name
generation.
I have been thinking that this code should be moved back into the jdbc
connector object... but that is for another day.
-dain
----- Original Message -----
From: "David Jencks" <[EMAIL PROTECTED]>
To: <[EMAIL PROTECTED]>
Sent: Sunday, August 26, 2001 11:20 PM
Subject: Re: [JBoss-dev] SQL reserved words
> Probably I don't understand all the issues here,
>
>
> Why not just use the fully qualified column name relation_name.column_name
> always and dispense with aliases? You can't use a reserved word for a
> relation_name anyway, so you don't really need to worry about keeping
track
> of them... the db will complain.
>
> If you do want to keep track of reserved words, there is a database
> metadata method getSQLKeywords that might be helpful.
>
> david jencks
>
> On 2001.08.26 17:52:35 -0400 Dain Sundstrom wrote:
> > Hi all,
> >
> > I have been thinking over the issue of generation of table aliases in
> > EJB-QL
> > queries, and have run into some problems. What I want to do is prevent
> > the
> > EQL-QL assembler from generating table aliases that have been already
> > used,
> > that are reserved words, or are a db object name (i.e., a table, view,
or
> > other name). I can handle the first to easily, but I can't think of a
> > way
> > to prevent collision with db objects.
> >
> > We could just tell users that they can prevent the code from generating
> > an
> > alias that is the name of a db object by adding the name to a reserved
> > word
> > list in the config file. I think this is reasonable as long as it is
> > rare.
> >
> > Then there is the issue of generating a database alias that it the same
> > as
> > an auto generated table name. This can happen because there is no
> > central
> > repository for the reserved word list. Let me explain the last claim a
> > little more. I am proposing adding a reserved word list to the
> > type-mapping
> > section section of the config file. The type mapping is selectable on a
> > per
> > bean level (newer feature). This means that each bean effectively has
> > it's
> > own datasource mapping information, and no central repository.
> >
> > Again, I think the only way around this is to have the user hand assign
> > the
> > table name and if collision persists add the table name to the reserved
> > list.
> >
> > I just don't like the idea of forcing users to do a lot of hand
> > configuration of the data mapping. I think the system should basically
> > work
> > without any jboss specific configuration of the cmp engine.
> >
> > If you have any insight into this issue, please speak-up.
> >
> > -dain
> >
> >
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> >
> >
>
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