提高CURSOR FOR LOOP的效率

Question

I have two CURSOR FOR LOOPS, one to find AVG(USAGE) on public holidays, the other to find AVG(USAGE) on ordinary days. Info retrieved from these is written into another table. It runs rather slowly, and I'm sure there must be a way to improve efficiency, but I'm still pretty new at this and I suspect my code is clunky, at best.

create or replace PROCEDURE USAGE_FORECAST AS
  v_dayNumber NUMBER;  
  v_halfHour NUMBER;

  CURSOR c_nonPublicHoliday is
    SELECT STREET, SUBURB, DAY, HH, AVG(USAGE) AVG_USAGE
      FROM INITIAL_TABLE, HOLIDAY_TABLE
      WHERE (to_char(day, 'd') = v_dayNumber
             OR to_char(day, 'd') = v_dayNumber-7)
            AND INITIAL_TABLE.DAY IN (SELECT HOLIDAY_DATE FROM HOLIDAY_TABLE)
            AND HH = v_halfHour
      GROUP BY STREET, SUBURB, DAY, HH;

  CURSOR c_publicHoliday is
    SELECT STREET, SUBURB, DAY, HH, AVG(USAGE) AVG_USAGE
      FROM INITIAL_TABLE, HOLIDAY_TABLE
      WHERE V_NEM_RM16.DAY IN (SELECT HOLIDAY_DATE FROM HOLIDAY_TABLE)
            AND HH = v_halfHour
      GROUP BY STREET, SUBURB, DAY, HH;                             

BEGIN
  FOR v_forecastDay IN 1..7 LOOP
    v_dayNumber := v_forecastDay;

    FOR v_halfHourInterval IN 1..48 LOOP
      v_halfHour := v_halfHourInterval;

      FOR R1 IN c_nonPublicHoliday LOOP
        INSERT INTO LOCAL_TABLE
          (STREET,    SUBURB,    DAY,     HH,    USAGE)
        VALUES
          (R1.STREET, R1.SUBURB, SYSDATE, R1.HH, R1.AVG_USAGE);
      END LOOP;

      FOR R1 IN c_PublicHoliday LOOP
        INSERT INTO LOCAL_TABLE
          (STREET,    SUBURB,    DAY,  HH,       USAGE)
        VALUES
          (R1.STREET, R1.SUBURB, SYSDATE, R1.HH, R1.AVG_USAGE);
      END LOOP;
    END LOOP;
  END LOOP;

Now, at the moment, it's running both CURSOR FOR loops regardless of whether the day is a public holiday or not. I'm sure there's a way to structure my select statement(s) so that this isn't necessary, but it's beyond me at the moment. Secondly, I suspect the Public Holiday is returning too much information, but that may just be because there are a lot of public holidays in the next week here in Aus.

Answer 1

I modify your query, however you have to check it.

create or replace PROCEDURE USAGE_FORECAST AS
  v_dayNumber NUMBER;  
  v_halfHour NUMBER;

  CURSOR c_nonPublicHoliday is
    SELECT STREET, SUBURB, DAY, HH, AVG(USAGE) AVG_USAGE
      FROM INITIAL_TABLE, HOLIDAY_TABLE
      WHERE (to_char(day, 'd') = v_dayNumber
             OR to_char(day, 'd') = v_dayNumber-7)
            /*AND INITIAL_TABLE.DAY IN (SELECT HOLIDAY_DATE FROM HOLIDAY_TABLE)*/
            AND exists (SELECT 1 FROM HOLIDAY_TABLE h where h.HOLIDAY_DATE  = INITIAL_TABLE.DAY )
            AND HH = v_halfHour
      GROUP BY STREET, SUBURB, DAY, HH;

  CURSOR c_publicHoliday is
    SELECT STREET, SUBURB, DAY, HH, AVG(USAGE) AVG_USAGE
      FROM INITIAL_TABLE, HOLIDAY_TABLE
      WHERE /*V_NEM_RM16.DAY IN (SELECT HOLIDAY_DATE FROM HOLIDAY_TABLE)*/
            exists (SELECT 1  FROM HOLIDAY_TABLE H where H.HOLIDAY_DATE = V_NEM_RM16.DAY)
            AND HH = v_halfHour
      GROUP BY STREET, SUBURB, DAY, HH;                             

BEGIN
  FOR v_forecastDay IN 1..7 LOOP
    v_dayNumber := v_forecastDay;

    FOR v_halfHourInterval IN 1..48 LOOP
      v_halfHour := v_halfHourInterval;

      FOR R1 IN c_nonPublicHoliday LOOP
        INSERT INTO LOCAL_TABLE
          (STREET,    SUBURB,    DAY,     HH,    USAGE)
        VALUES
          (R1.STREET, R1.SUBURB, SYSDATE, R1.HH, R1.AVG_USAGE);
      END LOOP;

      FOR R1 IN c_PublicHoliday LOOP
        INSERT INTO LOCAL_TABLE
          (STREET,    SUBURB,    DAY,  HH,       USAGE)
        VALUES
          (R1.STREET, R1.SUBURB, SYSDATE, R1.HH, R1.AVG_USAGE);
      END LOOP;
    END LOOP;
  END LOOP;