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Data can exist in many different places. Instead of moving data to a single database, the BI Server can access multiple databases simultaneously to answer a single query, regardless of whether the databases are from different vendors or what version of database software each runs under.

When the BI Server accesses heterogeneous databases, it handles automatically

• database operations such as
  • sort
  • and join (known as stitch join)
• and required transformation, such as:
  • data type casting
  • or applying multiple complex functions.

The BI server can access a large of data sources included XML.

This capability is also called:

• Federated Query
• Federation
• Multi-Database Access
• Cross-Database Join

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Example

An example : OBIEE - Federated Query with Excel Sheet where you have two data source :

• one Excel used to store the quota
• an other Oracle where the datawarhouse is located

DWH and OLTP reconciled

A datawarehouse is never completely up-to-date because an extraction is performed periodically.

OBIEE is able to :

• perform a query against your OLTP application system to retrieve the data from the last extraction
• perform a query against the DWH system
• and to merge the two query in on result