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In the theory of [[relational databases]], a '''Boolean conjunctive query''' is a [[conjunctive query]] without distinguished predicates, i.e., a query in the form <math>R_1(t_1) \wedge \cdots \wedge R_n(t_n)</math>, where each <math>R_i</math> is a relation symbol and each <math>t_i</math> is a [[tuple]] of variables and constants; the number of elements in <math>t_i</math> is equal to the [[arity]] of <math>R_i</math>. Such a query evaluates to either true or false depending on whether the relations in the database contain the appropriate tuples of values, i.e. the conjunction is [[Validity (logic)|valid]] according to the facts in the database.
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