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Chapter 12. DDL Metadata

12.1. DDL Metadata
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A VDB can define models/schemas using DDL. Here is a small example of how one can define a view inside the -vdb.xml file. See the <metadata> element under <model>.

Example 12.1. Example to show view definition

<model visible = "true" type = "VIRTUAL" name = "customers">
     <metadata type = "DDL"><![CDATA[
              CREATE VIEW PARTS (
                   PART_ID integer PRIMARY KEY,
                   PART_NAME varchar(255),
                   PART_COLOR varchar(30),
                   PART_WEIGHT varchar(255)
               ) AS
                  select a.id as PART_ID, a.name as PART_NAME, b.color as PART_COLOR, b.weight as PART_WEIGHT from modelA.part a, modelB.part b where a.id = b.id
     ]]>
     </metadata>
</model>
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Another complete DDL based example is at the end of this section.

Note

The declaration of metadata using DDL, NATIVE or DDL-FILE is supported out of the box, however the MetadataRepository interface allows users to plug-in their own metadata facilities. For example, you can write a Hibernate based store that can feed the necessary metadata. You can find out more about custom metadata repositories in Red Hat JBoss Data Virtualization Development Guide: Server Development.

Note

The DDL based schema is not constrained to be defined only for the view models.

Note

The full grammar for DDL is in the appendix.
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