How can we optimize SQL query to fetch data from Salesforce Database?

As Salesforce doesn’t save data in traditional way. Data of all tenants are in common table, so traditional Query optimization query and technique will not work in this case, so there is no such tool available to optimize final generated SQL. We only have option to create SOQL which is optimized by custom inbuilt Force.com Query Optimizer.

In Summer14, Salesforce released Query Plan Tool to analyze how query is performing. With help of this tool, we can get an idea how we can change our query to perform better.