Somewhat surprisingly most web developers I know know very little SQL, having picked it up exclusively by tinkering to get things done any way whatsoever, even if clumsy or slow. In fact SQL might look deceptively simple at times, at one point I read an ANSI SQL book so I already had some formal education in SQL when I started doing webdev, but I only really learnt ANSI SQL at the university in the databases course, and then I still had to do more learning about many details of my DB server of choice (postgres), including things like spatial queries and indexes, full-text search etc., you can get huge speed ups and infrastructure simplifications by putting those kinds of things directly in the DB.
Ask people about difference between LEFT JOIN and RIGHT JOIN, or using the schema from the article, to select all attributes of employees with the highest salary in their department in pure SQL and you will see how much or how little people know, in fact many webdevs don't even understand JOINs at all!
Ask people about difference between LEFT JOIN and RIGHT JOIN, or using the schema from the article, to select all attributes of employees with the highest salary in their department in pure SQL and you will see how much or how little people know, in fact many webdevs don't even understand JOINs at all!