First of all, why the Cobol reference? Yes, SQL is embeddable in Cobol, but the article never touched on that.
'Proper SQL' - what's that then? The opposite of 'improper SQL' perhaps?
Mainframe-derived SQL was/is/should probably be written in CAPS, whereas *nix-derived SQL should probably be lower case. Mixed case? Ugh! Windows-derived SQL? Who cares.
Why mix database design/normalisation and SQL as topics? The two only come together after mucho-arguing when it's time to finally, like, lay down a schema. Even then the modern-fangled way is to use a modelling tool to do the doing, often in complete ignorance of DBMS-specific best practices . Pah!
Is S.Q.L. (never, ever, ever 'sequel', that's a follow-up) even a language? Not in my book.
Triggers - dangerous? Agreed. Also often expensive. They don't get a look-in on big-data MPP systems.
Remember, neat SQL is efficient SQL ;-)