Microsoft has released previews of SQL Azure, the database for its Azure cloud infrastructure platform, and SQL Server StreamInsight, its entry in the CEP (complex event processing) arena.

The company has also announced a SQL Server driver that provides Azure support for PHP, a language popular among web application developers. MSDN and Technet subscribers have also gained access to the previews; they will be generally available later today.

SQL Azure Database is available at no charge until Azure's commercial launch in November, at which point it will be offered in two tiers. The web edition will cost US$9.99(£6) a month and allow up to 1GB of data, while the Business Edition will include up to 10GB and cost $99.99 per month, according to an official blog post.

The software represents a subset of SQL Server 2008's capabilities, according to Forrester Research analyst James Kobielus.

"This is a proof-of-concept that SQL Server can be ported to the cloud and support some advanced analytics that would be expensive if deployed on premises," Kobielus said.

Meanwhile, SQL Server StreamInsight, which will compete with CEP technologies from the likes of Tibco and IBM, focuses on finding insights from real-time information.

CEP software analyses streams of transactions looking for certain patterns or correlations, subsequently triggering a response if required. For example, it is used by financial institutions for rapid-fire stock trading, and e-commerce sites for fraud detection.

While the CEP market remains fairly small, observers expect it will grow quickly in coming years.

StreamInsight will be shipping as part of SQL Server 2008 R2, which is expected to be available in the first half of next year, according to a blog post.