Oracle C++ Call Interface Programmer's Guide

Describing Database Metadata
You obtain metadata by calling the getMetaData method on the Connection
class in case of an explicit describe, or by calling the getColumnListMetaData
method on the ResultSet class to get the metadata of the result set columns. Both
methods return a MetaData object with the described information. The MetaData
class provides the getxxx methods to access this information.
Notes on Types and Attributes
When performing DESCRIBE operations, be aware of the following issues:
■ The ATTR_TYPECODE returns typecodes that represent the type supplied when
you created a new type by using the CREATE TYPE statement. These typecodes
are of the enumerated type OCCITypeCode, which are represented by OCCI_
TYPECODE constants.
■ The ATTR_DATA_TYPE returns types that represent the datatypes of the
database columns. These values are of enumerated type OCCIType. For
example, LONG types return OCCI_SQLT_LNG types.
Describing Database Metadata
Note: Internal PL/SQL types (boolean, indexed table) are not
supported.
Describing database metadata is equivalent to an explicit DESCRIBE operation. The
object to describe must be an object in the schema. In describing a type, you call the
getMetaData method from the connection, passing the name of the object or a
RefAny object. To do this, you must initialize the environment in the OBJECT
mode. The getMetaData method returns an object of type MetaData. Each type of
MetaData object has a list of attributes that are part of the describe tree. The
describe tree can then be traversed recursively to point to subtrees containing more
information. More information about an object can be obtained by calling the
getxxx methods.
If you need to construct a browser that describes the database and its objects
recursively, then you can access information regarding the number of attributes for
each object in the database (including the database), the attribute ID listing, and the
attribute types listing. By using this information, you can recursively traverse the
describe tree from the top node (the database) to the columns in the tables, the
attributes of a type, the parameters of a procedure or function, and so on.
Metadata 6-3