Relational algebra and SQL

What is an algebra?


Analgebraconsists of a set ofatomic operands, and a set of operators.
We can form algebraicexpressionsby applying operators to operands
(which can be atomic or expressions themselves).

Example:
In the algebra of arithmetic, the atomic operands are constants and
variables, and the operators are +, -, /, and·.
Using these we can form expressions like((x+ 7)/(y−3)) +x.

Relational algebra

Relational algebra, defined in its basic form by E. F. Codd in 1970, has
relations as atomic operands, and various operations on relations (such as
select and join) as operators.
It is the mathematical basis of SQL queries.


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