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From Apache Wiki <wikidi...@apache.org>
Subject [Ws Wiki] Update of "Tuscany/TuscanyJava/DAS Java Overview/RDBDAS Java User Guide/Write Operation Ordering" by KevinWilliams
Date Mon, 02 Oct 2006 17:35:19 GMT
Dear Wiki user,

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The following page has been changed by KevinWilliams:
http://wiki.apache.org/ws/Tuscany/TuscanyJava/DAS_Java_Overview/RDBDAS_Java_User_Guide/Write_Operation_Ordering

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  Relational databases often use [http://en.wikipedia.org/wiki/Referential_integrity Referential
Integrity (RI)] constraints to maintain database consistency. When RI is enabled, database
operations must be performed in a specific order that prevents invalid references. If this
order is not adhered to then the database will throw an exception rather than let the write
succeed.
  
- When an application makes modifications to a data graph and then asks the RDB DAS to "apply
changes", the DAS will create a "batch" of database writes that must be sorted and the executed
in the correct order to avoid RI Constraint exceptions.  A simple example will help here.
 Assume a database with two tables CUSTOMER and ORDER.  Also assume that the ORDER table has
a [http://en.wikipedia.org/wiki/Foreign_key foreign key] reference to the CUSTOMER table.
 Now assume that the application has made modifications to a data graph that was retrieved
by the DAS using a SELECT statement like the following:
+ When an application makes modifications to a data graph and then asks the RDB DAS to "apply
changes", the DAS will create a "batch" of database writes that must be sorted and then executed
in the correct order to avoid RI Constraint exceptions.  A simple example will help here.
 Assume a database with two tables CUSTOMER and ORDER.  Also assume that the ORDER table has
a [http://en.wikipedia.org/wiki/Foreign_key foreign key] reference to the CUSTOMER table.
 Now assume that the application has made modifications to a data graph that was retrieved
by the DAS using a SELECT statement like the following:
  
  {{{
     SELECT * FROM CUSTOMER LEFT JOIN ORDER ON CUSTOMER.ID = ORDER.CUSTOMER_ID WHERE CUSTOMER.NAME
= ?

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