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Tuple relational calculus describes query answers by predicates over database tuples rather than a sequence of storage operations. A set-builder expression $\{t:P(t)\}$ returns tuples satisfying a formula built from relation membership, attribute comparisons, logical connectives and quantifiers. For example,selects employee tuples whose salary exceeds100. A join can be expressed using existentially quantified tuples from two relations and equality of their shared identifying attribute.

The formula needs a safety restriction. Over an unrestricted infinite value universe, a query such as $\{t:\neg \mathrm{Employee}(t)\}$ can demand infinitely many absent tuples. Safe tuple relational calculus restricts results to information grounded in the input and explicit constants. Under the usual finite-relation assumptions, its expressive power agrees with relational algebra. This gives a declarative query language while leaving the database system free to choose an efficient query plan.