[Opensource] DBObjects limitations

[Kenneth Tang]

Hi Paulo,

Can you elaborate more on the idea binding view to DBObject!?

Cheers,
Kenneth

----- Original Message -----
From: "Paulo Dias" <paulojorge.dias at edinfor.edp.pt>
To: <opensource at jcorporate.com>
Cc: <opensource-admin at jcorporate.com>
Sent: Tuesday, December 17, 2002 5:17 PM
Subject: Re: [Opensource] DBObjects limitations


>
> I advise you to create database views in order to hide the sql complexity,
> and the use DBObject as if it is a simple table.
> Trying to match database complex relations out of database world is very
> hard and a waste of time.
>
> Paulo Dias
> ACE Sistemas Comerciais
> (+351)210054200
> http://www.ace-sc.com
>
>
> |--------+------------------------------->
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> |        |          2002-12-16 02:54 PM  |
> |        |          Please respond to    |
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>   |       Subject:     [Opensource] DBObjects limitations
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>
>
>
>
> I am pretty new to Expresso framework, trying to port from a system that
> was not
> using persistence layer, and had  several problems with using DBObjects.
> Not
> sure if its DBObjects problem or me being a newbie.
> Could somebody help, please?
>
> 1. Setting up UPPER,LOWER, UNIQUE, DECODE
> We were not able to use SQL function like UPPER,LOWER, UNIQUE, DECODE etc.
>
> 2. Setting Complex WHERE conditions
> Complex WHERE condition needs to be set as
>     custList.setCustomWhereClause("CustomerType = \"AA"\ OR CustomerType =
> \"BA"
> \");
> As you can see, we need to generate the WHERE condition with column names
> and
> other details. This means, the SQL statements with specific COLUMN_NAME
> will be
> present in JAVA classes. (Note: These are Business Component java classes
> and
> not DB objects). Any changes to the database/tables, will have impact on
> both DB
> Object and Business Component JAVA classes.
> For Example, we will have to build the SQL WHERE condition as follows
> inside our
> search
>        s.sco_id = a.sco_id
>  and s.sco_id = l.sco_id
>  and l.country_iso3 in ('AFG')
>  and a.start_year >= '1995'
>  and a.start_year <= '1996'
>  and s.sco_id = sec.sco_id
>  and s.org_harmonized_char in
> ('UNRF','UNRI','UNRW','UNSO','UNTA','UNUE','UNUN','UNVL','UPUN','UTRA',
>
'WFPR','WHOR','WIPO','WMOR','WTOR','UNIT','UAID','UCAP','UNAI','UNAS','UNCC'
,'UNCD',
>
>
'UNCH','UNCR','UNCT','UNDC','UNDE','UNDM','UNDP','UNEP','UNES','UNFD','UNFF'
,'UNFP','UNFS',
>
>
'UNHC','UNHQ','UNHR','UNIA','UNIC','UNID','UNIF','PAHO','ITUN','ECAF','ECEU'
,'CLAD','FAOR',
>
> 'ESCA','ESCW','IAEA','ICAO','IFAD','ILOR','IMOR','IOCO','ITCE')
>
> Any change to the tables, we need to change the JAVA classes to reflect
the
> same.
>
> 3. Virtual table selects / INNER SELECT statements
> We use inner SELECT statements to get the specified range of records. This
> is
> not possible in DB Objects as the end result is coming from a virtual
> table.
> (Note : DB Object only offers a mechanism to limit the number of records
> retrieved (TOPN). )
> This means if we need to display records from 401 to 450, then we need to
> take
> the records till 450 and ignore the records from 1-400. In the existing
> implementation, we eliminate the 1-400 records in the database itself.
> Serious
> performance issue
> Thanks
> Irakli
>
>
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