Boolean conjunctive query

In the theory of relational databases, a Boolean conjunctive query is a conjunctive query without distinguished predicates, i.e., a query in the form R 1 ( t 1 ) ∧ ⋯ ∧ R n ( t n ) {\displaystyle R_{1}(t_{1})\wedge \cdots \wedge R_{n}(t_{n})} , where each R i {\displaystyle R_{i}} is a relation symbol and each t i {\displaystyle t_{i}} is a tuple of variables and constants; the number of elements in t i {\displaystyle t_{i}} is equal to the arity of R i {\displaystyle R_{i}} . 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.

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