SQL - optimize peformance by limiting table full scans

There's an excellent article here about using the PIVOT/UNPIVOT keywords in Oracle to organize and report data:
https://dzone.com/articles/impress-your-coworkers-by-using-sql-unpivot

However, I think the most interesting message here is how to limit your full table scans and thus enhance the DB access performance. So, read on ! Thanks Lukas Eder for the great article !