relational calculus - An operational methodolgy, founded on predicate calculus, dealing with descripitive expressions that are equivalent to the operations of relational algebra. Codd's reduction algorithm can convert from relational calculus to relational algebra.
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дс тдрлими цюлютдажкию дроемжки аиакиохдйис лидр
http://foldoc.doc.ic.ac.uk/foldoc/foldoc.cgi;
