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Doubt - Oreilly - Page 107

 
Niranjan Deshpande
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Hi all,

Plesae refer Oreilly - Page 107

All the three things - pkColumnName valueColumnName pkColumnValue are confusing me.

Functionally, what is the difference between these three.

It would be great if some one draws a relevant table here and explains me
 
Alex Kikhtenko
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Originally posted by Niranjan Deshpande:
Hi all,

Plesae refer Oreilly - Page 107

All the three things - pkColumnName valueColumnName pkColumnValue are confusing me.

Functionally, what is the difference between these three.

It would be great if some one draws a relevant table here and explains me


The schema is simple as a pie.

Have a look at the following table:



So, the layout is:
pkColumnName = "PK_COLUMN"
valueColumnName = "VALUE_COLUMN"
pkColumnValue = "DETERMINANT2" (for example)

The idea is each row in the table represents certain entity and there must be the way to distinguish between entities (3 entities in the preceding example)
[ February 09, 2008: Message edited by: Alex Kikhtenko ]
 
Niranjan Deshpande
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Thanks for that..

But its still unclear to me !!

Please explain the schema keeping in mind the example entiy in oreilly.
Will be grateful

What is the CUST_ID in the Oreilly code? Please explain the schema with reference to the code in the book
 
Alex Kikhtenko
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Ok. Let's consider the book's example with Customer entity.



Suppose we have another one entity Product:


As you can see we want the both entities to use the same table GENERATOR_TABLE to hold their Primary-Key-Next-Value.

Suppose also we've just persisted 3 Customer entities and 8 Product entities into the DB.

In this case the GENERATOR_TABLE table would look like:


So obviously CUST_ID is necessary to distinguish it's primary key value from primery key value of Product entity bean.

Hope this helps.
 
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