Groups > comp.lang.java.databases > #239

Re: Java Toplink Essentia

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From	"Lew" <lew@THRWHITE.remove-dii-this>
Subject	Re: Java Toplink Essentia
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  To: comp.lang.java.databases
nicola wrote:
>> In my db there are some tables like
>>
>> TABLE1_2006 (ID, CODE, VOLUME)
>> TABLE2_2007 (ID, CODE, VOLUME)
>> TABLE3_2008 (ID, CODE, VOLUME)

Martin Gregorie wrote:
> Declare a view  over all the tables and enquire on that.
> 
> But, why on earth use multiple tables? They don't do anything that a 
> single table with a YEAR column couldn't do while managing to make at 
> least one task more difficult as you've just demonstrated.

I feel suspicion when I read about inherited tables in a DBMS, such as in 
Postgres.  At first blush the OP's situation seemed to me like an 
inherited-table scenario.  I felt about as I might encountering an escaped 
specimen from Dr. Moreau's island.

I used to feel that way about automated object-relational mapping (ORM) 
packages, but JPA alleviates that.  There is a dichotomy between the world 
view of object-oriented programming and that of relational database 
architecture.  Inherited tables seem out of place to me - object-oriented 
monstrosities in a data world.  Multiple identical tables are like that also - 
if the data structures are the same and have the same interpretation, that 
argues for a single logical table.  Martin's suggestion is spot on, and 
completely harmonious with the data-world outlook.

I don't know of a term analogous to "normal form" (as in "third normal form") 
for excessive splitting of tables into many tables; all the normal forms have 
to do with insufficient splitting.  Advances in the database world occur in 
how to structure data - relations, normal forms, star schemae, foreign keys, 
these are the building blocks of DBMSes as classes and objects are of O-O 
programming.

How one structures data for a database is different from how one structures 
objects for a program.

-- 
Lew

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Thread

Java Toplink Essential - "nicola" <nicola@THRWHITE.remove-dii-this> - 2011-04-27 15:22 +0000
  Re: Java Toplink Essentia "Martin Gregorie" <martin.gregorie@THRWHITE.remove-dii-this> - 2011-04-27 15:22 +0000
    Re: Java Toplink Essentia "Lew" <lew@THRWHITE.remove-dii-this> - 2011-04-27 15:22 +0000
      Re: Java Toplink Essentia "Arved Sandstrom" <arved.sandstrom@THRWHITE.remove-dii-this> - 2011-04-27 15:22 +0000

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