I think it's easy once you've got your head round the model of data sets but there are plenty of experienced programmers who, due to lack of experience with SQL

I think it's easy once you've got your head round the model of data sets but there are plenty of experienced programmers who, due to lack of experience with SQL, still drop back to iterating through large collections of data. It's the fastest way for them to solve a problem in terms of development effort, but it often leads to poor solutions and poor SQL.