sum() 和decode()使用

CREATE TABLE T82
(
    ID          NUMBER(4),
    DealDate    DATE,
    RESULT      VARCHAR2(20),
    Comments    VARCHAR2(20)
);

INSERT INTO T82 VALUES(1, to_date('2011-10-02', 'YYYY-MM-DD'), 'Y', NULL);
INSERT INTO T82 VALUES(2, to_date('2011-10-02', 'YYYY-MM-DD'), 'N', 'Reject');
INSERT INTO T82 VALUES(3, to_date('2011-10-02', 'YYYY-MM-DD'), 'Y', NULL);
INSERT INTO T82 VALUES(4, to_date('2011-10-02', 'YYYY-MM-DD'), 'N', 'Reject');
INSERT INTO T82 VALUES(5, to_date('2011-10-02', 'YYYY-MM-DD'), 'N', 'Reject');
INSERT INTO T82 VALUES(6, to_date('2011-10-02', 'YYYY-MM-DD'), 'Y', NULL);
INSERT INTO T82 VALUES(7, to_date('2011-10-03', 'YYYY-MM-DD'), 'N', 'Reject');
INSERT INTO T82 VALUES(8, to_date('2011-10-03', 'YYYY-MM-DD'), 'Y', NULL);
INSERT INTO T82 VALUES(9, to_date('2011-10-04', 'YYYY-MM-DD'), 'Y', NULL);
INSERT INTO T82 VALUES(10, to_date('2011-10-05', 'YYYY-MM-DD'), 'N', 'Reject');
INSERT INTO T82 VALUES(11, to_date('2011-10-05', 'YYYY-MM-DD'), 'Y', NULL);

查询结果要求：

        统计出在2011-10-02这一天里总的条目数，Y的数目，N的数目.
        结果集包含的字段是：DealDate,Y_Qty,N_Qty.

 select DEALDATE,
        count(*)  as Qty,
        sum(decode(RESULT,'Y',1,0))  as Y_Qty,
        sum(decode(RESULT,'N',1,0))  as N_Qty
 from   T82
 where  to_char(DEALDATE,'yyyy-mm-dd') = '2011-10-02'
 group by DEALDATE;