oracle中一个按月分组的方法

    最近项目中要出一个按月、周、日统计的报表

    某年按月分组：
    Sql代码
    SELECT A.D as label,NVL(B.NUM,0) AS value
     FROM
      (
  SELECT ROWNUM AS D FROM SYS_UNUSE WHERE ROWNUM < 13
      )  A
      LEFT JOIN
      (
     SELECT TO_CHAR(T.STARTTIME,'MM') AS D,COUNT(1) AS NUM FROM CALL_HIS T
     WHERE T.STARTTIME>=:prStartDate AND T.STARTTIME<:prEndDate
     GROUP BY TO_CHAR(T.STARTTIME,'MM')
      ) B ON A.D=B.D ORDER BY A.D

    某月按日分组：
    Sql代码
    SELECT A.D as label,NVL(B.NUM,0) AS value
     FROM
      (
  SELECT ROWNUM AS D FROM SYS_UNUSE WHERE ROWNUM <= TO_CHAR(LAST_DAY(:prDate),'DD')
      )  A
      LEFT JOIN
      (
     SELECT TO_CHAR(T.STARTTIME,'MM') AS D,COUNT(1) AS NUM FROM CALL_HIS T
     WHERE T.STARTTIME>=:prStartDate AND T.STARTTIME<:prEndDate
     GROUP BY TO_CHAR(T.STARTTIME,'MM')
      ) B ON A.D=B.D ORDER BY A.D

    按周统计：
    Sql代码
    SELECT A.D as label,NVL(B.NUM,0) AS value
     FROM
      (
  SELECT TO_CHAR(:prDate+ROWNUM-1,'yyyy-MM-DD') as D FROM SYS_UNUSE WHERE ROWNUM <= 7
      )  A
      LEFT JOIN
      (
     SELECT TO_CHAR(T.STARTTIME,'yyyy-MM-DD') AS D,COUNT(1) AS NUM FROM CALL_HIS T
     WHERE T.STARTTIME>=:prStartDate AND T.STARTTIME<:prEndDate
     GROUP BY TO_CHAR(T.STARTTIME,'yyyy-MM-DD')
      ) B ON A.D=B.D ORDER BY A.D

    说明：SYS_UNUSE表是一个没用的表，跟业务没有任何关系，表里只有100条数据，我这里是足够用了。