The database structural query language SQL implements ternary logic as
a means of handling comparisons with NULL field content. For the NULL
in SQL an actual value is either true or false, but is not currently recorded
in the database (unknown). To take care of this, a ternary logic suggested
is as follows. The third state Unknown (U) represents the truth value : either
true or false. Extension of Boolean NOT for U will be, NOT (U) = U and
that for Boolean OR will be S OR U = Max(S, U) where S is the truth value
of a given statement and T > U > F holds. What would be U F ?
(A) T
(B) F
(C) U
(D) data is inadequate for computing
