函数，传进两个时间，返回工作时间

CREATE OR REPLACE FUNCTION FUN_GET_HOUR(STARTTIME IN VARCHAR2,ENDTIME IN VARCHAR2)RETURN NUMBER
IS
 N_DAY NUMBER;--相隔天数
 V_START_DAY VARCHAR2(10):=SUBSTR(STARTTIME,1,10);
 V_END_DAY VARCHAR2(10):=SUBSTR(ENDTIME,1,10);
 V_START_TIME VARCHAR2(10):=SUBSTR(STARTTIME,12);
 V_END_TIME VARCHAR2(10):=SUBSTR(ENDTIME,12);
 UP_TIME VARCHAR2(10):='08:30:00';
 DOWN_TIME VARCHAR2(10):='17:30:00';
 N_TIMER NUMBER;
 N_MINUTE NUMBER;
 N_HOURS NUMBER;
 N_SECOND NUMBER;
BEGIN
 SELECT TO_DATE(V_END_DAY,'YYYY-MM-DD')-TO_DATE(V_START_DAY,'YYYY-MM-DD') INTO N_DAY FROM DUAL;
 N_DAY:=N_DAY+1;
 IF N_DAY = 1 AND V_START_TIME < UP_TIME AND V_END_TIME < UP_TIME THEN
    RETURN 0;
 END IF;
 FOR X IN 1..N_DAY LOOP
   IF X=1 THEN
     IF V_START_TIME > DOWN_TIME  THEN
       N_TIMER:=0;
     ELSE
       IF V_START_TIME < UP_TIME THEN
         V_START_TIME:=UP_TIME;
       END IF;
       IF N_DAY = 1 AND DOWN_TIME > V_END_TIME THEN
         DOWN_TIME:=V_END_TIME;
       END IF;
       N_MINUTE:=TO_NUMBER(TO_CHAR(TO_DATE(DOWN_TIME,'HH24:MI:SS'),'MI'))-TO_NUMBER(TO_CHAR(TO_DATE(V_START_TIME,'HH24:MI:SS'),'MI'));
       N_HOURS:=TO_NUMBER(TO_CHAR(TO_DATE(DOWN_TIME,'HH24:MI:SS'),'HH24'))-TO_NUMBER(TO_CHAR(TO_DATE(V_START_TIME,'HH24:MI:SS'),'HH24'));
       N_SECOND:=TO_NUMBER(TO_CHAR(TO_DATE(DOWN_TIME,'HH24:MI:SS'),'SS'))-TO_NUMBER(TO_CHAR(TO_DATE(V_START_TIME,'HH24:MI:SS'),'SS'));
       N_TIMER:=N_MINUTE*60+N_HOURS*60*60+N_SECOND;--提交的时间
     END IF;
   ELSIF X=N_DAY THEN
     IF V_END_TIME < UP_TIME THEN
       N_TIMER:=N_TIMER+0;
     ELSE
       IF V_END_TIME > DOWN_TIME THEN
         V_END_TIME:=DOWN_TIME;
       END IF;       
       N_MINUTE:=TO_NUMBER(TO_CHAR(TO_DATE(V_END_TIME,'HH24:MI:SS'),'MI'))-TO_NUMBER(TO_CHAR(TO_DATE(UP_TIME,'HH24:MI:SS'),'MI'));
       N_HOURS:=TO_NUMBER(TO_CHAR(TO_DATE(V_END_TIME,'HH24:MI:SS'),'HH24'))-TO_NUMBER(TO_CHAR(TO_DATE(UP_TIME,'HH24:MI:SS'),'HH24'));
       N_SECOND:=TO_NUMBER(TO_CHAR(TO_DATE(V_END_TIME,'HH24:MI:SS'),'SS'))-TO_NUMBER(TO_CHAR(TO_DATE(UP_TIME,'HH24:MI:SS'),'SS'));
       N_TIMER:=N_TIMER+N_MINUTE*60+N_HOURS*60*60+N_SECOND;
     END IF;
   ELSE
     N_MINUTE:=TO_NUMBER(TO_CHAR(TO_DATE(DOWN_TIME,'HH24:MI:SS'),'MI'))-TO_NUMBER(TO_CHAR(TO_DATE(UP_TIME,'HH24:MI:SS'),'MI'));
     N_HOURS:=TO_NUMBER(TO_CHAR(TO_DATE(DOWN_TIME,'HH24:MI:SS'),'HH24'))-TO_NUMBER(TO_CHAR(TO_DATE(UP_TIME,'HH24:MI:SS'),'HH24'));
     N_SECOND:=TO_NUMBER(TO_CHAR(TO_DATE(DOWN_TIME,'HH24:MI:SS'),'SS'))-TO_NUMBER(TO_CHAR(TO_DATE(UP_TIME,'HH24:MI:SS'),'SS'));
     N_TIMER:=N_TIMER+N_TIMER+N_MINUTE*60+N_HOURS*60*60+N_SECOND;
   END IF;
 END LOOP;
 RETURN N_TIMER;
END FUN_GET_HOUR;