Building the queries is the easy part. Making the queries run fast with large tables is difficult and there are trainings available, but very focused and a bit

Building the queries is the easy part. Making the queries run fast with large tables is difficult and there are trainings available, but very focused and a bit expensive compared with the ones on large training websites (ex. LinkedIn Learning). For example Brent Ozar (brentozar.com) has lots of blogs and 2 sets of trainings for MS SQL Server, some for beginners and some for experts, that are extremely useful for people with such needs. Problem is, expert tuning for MS SQL is totally different than expert tuning Oracle that is totally different than Postgres and others. On a side note, if you have to join 15 tables for a report it is a sign you may go in the wrong direction. In 99% of the cases I never needed more than 5-6 tables if the data is well structured, but that takes years to learn.