Verifique se há datas sobrepostas em qualquer linha de uma tabela Oracle SQL

CREATE OR REPLACE TRIGGER TRGEPOCASNAOSOBREPOSTAS
    AFTER INSERT OR UPDATE
    ON EPOCA
  c INTEGER;
BEGIN
    SELECT COUNT(*)
    INTO c
    FROM EPOCA e
    WHERE EXISTS (
        SELECT 1
        FROM EPOCA ee 
        WHERE (e.DATA_INI BETWEEN ee.DATA_INI AND ee.DATA_FIM 
              OR e.DATA_FIM BETWEEN ee.DATA_INI AND ee.DATA_FIM) 
           AND ee.ROWID <> e.ROWID);

    IF c > 0 THEN
            RAISE_APPLICATION_ERROR(-20021, 'INSERT FAILED BECAUSE SELECTED DATES OVERLAP EXISTENT ONES');
    END IF;
END;