> A related piece of advice is: Learn the relational model first, SQL second (doing it the other way around is hard). Finally, read either or both of Ted Codd’s first two papers every year. (Those papers are “Derivability, Redundancy, and Consistency of Relations Stored in Large Data Banks”, IBM Research Report RJ599, August 19th, 1969, reprinted in ACM SIGMOD Record 38, No. 1 (March 2009), and “A Relational Model of Data for Large Shared Data Banks”, CACM 13, No. 6, June 1970, which you can find online.)
Ed:
DERIVABILITY, REDUNDANCY CONSISTENCY OF RELATIONS STORED IN LARGE DATA BANKS E. F. Codd:
Somewhat related, this interview with Date on the relational model:
https://www.red-gate.com/simple-talk/opinion/opinion-pieces/...