A SQL statement involving two or more tables requires Oracle join data from multiple sources in order to achieve the desired result. The Oracle Server has several built in methods for performing joins, and each method has its own performance and resource usage qualities. While an application developer or DBA doesn’t need to explicitly tell Oracle which join method to use or the order in which different tables should be joined, a solid understanding of how Oracle processes joins allows us to design and build systems for optimal performance. In this presentation we’ll examine the different methods Oracle uses for joining data from multiple sources, and we’ll see how this understanding can be used to design better database schemas, tune SQL statements, and tune databases as a whole for better join performance. Since most SQL statements involve joins, tuning joins leads to improved overall system performance.
how to tune the joins?