Relational Theory for Computer Professionals: 
There are literally hundreds of books on relational theory or the SQL language, or both. But this one is different. First, nobody is more qualified than Chris Date to write such a book; Ted Codd, inventor of the relational model, and he were colleagues for many years, and his involvement with the technology goes all the way back to the time of Codd’s very first papers, in 1969-1970. Second, most books try to use SQL as a vehicle for teaching relational theory, but this book very deliberately takes the opposite approach. Its primary aim is to teach relational theory as such.
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