CREATE TABLE BRON (
    OBJ     INTEGER NOT NULL,
    DATA    DATE NOT NULL,
    H1      INTEGER NOT NULL,
    H2      INTEGER,
    STATUS  VARCHAR(20) NOT NULL
);

ALTER TABLE BRON ADD CONSTRAINT UNQ1_BRON UNIQUE (OBJ, DATA, H1);

ALTER TABLE BRON ADD CONSTRAINT FK_BRON_1 FOREIGN KEY (OBJ, DATA, H2) REFERENCES BRON (OBJ, DATA, H1);

-- *********************

INSERT INTO BRON (OBJ, DATA, H1, H2, STATUS) VALUES (1, '10-JUN-2018', 8, 12, 'busy');
INSERT INTO BRON (OBJ, DATA, H1, H2, STATUS) VALUES (1, '10-JUN-2018', 12, 16, 'free');
INSERT INTO BRON (OBJ, DATA, H1, H2, STATUS) VALUES (1, '10-JUN-2018', 16, NULL, 'busy');
INSERT INTO BRON (OBJ, DATA, H1, H2, STATUS) VALUES (2, '11-JUN-2018', 8, 16, 'busy (весь день)');
INSERT INTO BRON (OBJ, DATA, H1, H2, STATUS) VALUES (2, '11-JUN-2018', 16, 16, 'free (как вариант)');

create or alter trigger bron_biu0 for bron
active before insert or update position 0
as
BEGIN
   IF ((new.status <> 'free') and
      (exists(select 1 from BRON b
              where (b.obj = new.obj) and (b.data = new.data)
                       and (new.h1 between b.h1 and b.h2)
             ))) then
     exception BOOM new.h1;
END