Domain Constraint (Databases)

The domain constraint is an implicit constraint that every value in a tuple must be from the domain of its attribute.

Each value in a tuple must be from the domain of the attribute for that column. If $t=<v_1,v_2,...,v_n>$, in relation state $r$ of $R(A_1,A_2,...,A_n)$ then $v_i$ must be a value from the domain $\text{dom}(A_i)$.