oracle中一个按月分组的写法

最近项目中要出一个按月、周、日统计的报表

某年按月分组：

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：

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：

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。