Formal Relational Query Languages

Two mathematical Query Languages form the basis for “real” languages (e.g. SQL), and for implementation:

• Relational Algebra: More operational, very useful for representing execution plans.

• Relational Calculus: Lets users describe what they want, rather than how to compute it. (Non-operational, declarative.)

• Understanding Algebra & Calculus is key to

• understanding SQL, query processing!

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