Links and references
What the heck is going on with the datetime data type?
I’m not making that up about the accuracy! Here’s the documentation.
Confused about decimal and numeric data types?
I really like Aaron Bertrand’s discussion of them in his answer to this stackexchange question.
Mildly related: secret XRay glasses for your physical table structure
Ever wondered what happens behind the scenes when you do things like alter column types? Remus Rusanu shows you how to see the real physical structure of tables under the hood.