list of databases used by Internet’s biggest websites..

·         The king of scalability, Google, uses BigTable.

·         Facebook uses Hive (Data warehouse for Hadoop, supports tables and a variant of SQL called hiveQL) and Cassandra (Multi-dimensional, distributed key-value store) for Facebook's private messaging.

·         Yahoo uses modified PostgreSQL.

·         YouTube uses MySQL but they are moving to Google's BigTable.

·         Myspace uses SQL Server.

·         Twitter and Wikipedia uses MySQL.

·         Microsoft uses SQL Server, which is very obvious.

·         Flickr uses MySQL.