Thanks for this Stairway!
I would add only a couple of references - background for the Relational Model:
Edgar F. Codd
https://en.wikipedia.org/wiki/Edgar_F._Codd
Codd, E. F. (1970). "A relational model of data for large shared data banks" (PDF). Communications of the ACM. 13 (6): 377. doi:10.1145/362384.362685.
http://www.seas.upenn.edu/~zives/03f/cis550/codd.pdf
- webrunner
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A SQL query walks into a bar and sees two tables. He walks up to them and asks, "Can I join you?"
Ref.: http://tkyte.blogspot.com/2009/02/sql-joke.html