Integration of  Heterogeneous Databases in Data Warehousing

Integration of  Heterogeneous Databases in Data Warehousing

We have two approaches to integrate two different heterogeneous databases.

• Query-driven Approach

• Update-driven Approach

Query-Driven Approach in Data Warehousing

Query-Driven Approach is the traditional approach to integrate heterogeneous databases. The Query-Driven Approach approach was used to build mediators on top of multiple heterogeneous databases. These mediators are also known as integrators.

Process of Query-Driven Approach

Process of Query-Driven Approach involves the following steps’

• To make a query to the client-side
• Translation of the query by the metadata dictionary. Metadata dictionary translates the query into a suitable form for different heterogeneous sites(that are involved in the integration process).
• Mapping of the queries are mapped
• Mapped queries must be sent to the local query processor.
• Collection of the results from different heterogeneous sites.
• Integration of all collected results into a global answer set.

Disadvantages of Query-Driven Approach in Data Warehousing

• The query-driven approach needs complex processes. Two common common complex processes are integration and filtering processes.
• If your quires are frequent, then a Query-driven approach is very expensive.
• The query-driven approach is also very expensive for queries that require aggregations.
• The query-driven approach is very inefficient.

Update Driven Approach  in Data Warehousing

Update-Driven Approach is an alternative to the traditional Query-Driven Approach. Nowadays, the latest data warehouse systems follow the update-driven approach. In an update-driven approach, the information from many heterogeneous sources is integrated in advance and then the information stored in a warehouse. This information is available and very helpful if we want to query and analyze the information directly.

Advantages of Update Driven Approach

This approach has the following advantages −

• Update-Driven Approach provides high performance.
• The following steps are must for data.
  • Copying the data
  • Processing the data
  • Integrating the data
  • Annotating the data
  • Summarizing the data
  • Restructuring the data.