[rswail]

> I know everything new such as unit testing, proper source control, dependency injection, linq and ORM tools. However, when it comes to speed of queries he is much better at optimization.

The reason he is better at optimization is because he is not using an ORM. ORMs are a leaky abstraction that loses the power of SQL for the limited benefit of slightly easier programming. They also tend to move things that in SQL would be a JOIN that is executed in the database back into code.

Data is not an object, much that some "modern" languages would prefer to lose the distinction, with ORMs and DTOs obfuscating it.

RDMSs are based on cohesive logic (set theory) and have been tuned and optimized by people to do the best possible automation of data storage and retrieval, while abstracting the very low level.

ORMs on the other hand, take the logic that should be at the data management level, including invariants and moves it into code that does what SQL does, but slowly and badly.