They are not too difficult in my opinion. Anyone with at least a year of SQL experience should be able to answer these more or less correct.
(and I'm just a measly BI developer :-D)
#3 might be a tad more difficult if you have never worked with triggers before. But then again, I almost never work with them and I immediately saw it cannot handle updates on multiple rows at the same time. 😉
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MCSE Business Intelligence - Microsoft Data Platform MVP