As application developers, your main focus is to design the most efficient queries for your application. You want to ensure the integrity of the data that your application pushes to the database, and construct the most efficient queries to retrieve the data needed for the application. In many cases, the application performance is deferred to a later stage of the development cycle. Often it is left to the database performance specialists who can provide the recommendations for the index design, which may also include query rewrite, in order to meet the performance requirement. But understanding the query’s performance can greatly improve productivity and help developers to seek a more performant solution early in the development cycle.
Database vendors understand this challenge, and enterprise-class RDBMSs include Performance Tuning capability as part of their database toolsets.