text: --
  -- Correlated issues.
  --
  CREATE TABLE rt_issues (
    issue_id int NOT NULL,
    host_id int default NULL,
    service_id int default NULL,
    start_time int NOT NULL,
  
    ack_time int default NULL,
    end_time int default NULL,
  
    PRIMARY KEY (issue_id),
    INDEX (start_time),
    UNIQUE (host_id, service_id, start_time),
    FOREIGN KEY (host_id) REFERENCES rt_hosts (host_id)
      ON DELETE CASCADE
  );
  CREATE SEQUENCE issues_seq
  START WITH 1
  INCREMENT BY 1;
  CREATE TRIGGER issues_trigger
  BEFORE INSERT ON rt_issues
  FOR EACH ROW
  BEGIN
    SELECT issues_seq.nextval INTO :NEW.issue_id FROM dual;
  END;
  /
  