Consider the general case of an OVERLAPS comparison, stated as follows.
(S1, E1) OVERLAPS (S2, E2)
The result of OVERLAPS is as follows.
(S1 > S2 AND NOT (S1 >= E2 AND E1 >= E2)) OR (S2 > S1 AND NOT (S2 >= E1 AND E2 >= E1)) OR (S1 = S2 AND (E1 = E2 OR E1 <> E2))
For Period data types or derived periods, where p1 is the first Period expression or derived period and p2 is the second Period expression or derived period, the values of S1, E1, S2, and E2 are as follows:
S1 = BEGIN(p1) E1 = END(p1) S2 = BEGIN(p2) E2 = END(p2)