使用场景:统计支出表中某人某年的每个月的支出情况
1.创建表如下（oracle）
--支出表
create table PAY
(
ID NUMBER(11) not null,
PAY_NAME VARCHAR2(100),
AUTHOR VARCHAR2(100),
TYPE_ID NUMBER(11),
PRICE FLOAT, --金额
BRIEF VARCHAR2(1000),
USERID NUMBER(11), --用户ID
TIMES DATE, --时间
PRIMARY KEY(ID)
)
2.插入测试数据
insert into PAY (ID, PAY_NAME, AUTHOR, TYPE_ID, PRICE, BRIEF, USERID, TIMES)
values (1, '1', '1', 0, 1, '1', 1, to_date('12-10-2012', 'dd-mm-yyyy'));
insert into PAY (ID, PAY_NAME, AUTHOR, TYPE_ID, PRICE, BRIEF, USERID, TIMES)
values (0, '3', '3', 1, 3, '3', 1, to_date('12-10-2012', 'dd-mm-yyyy'));
insert into PAY (ID, PAY_NAME, AUTHOR, TYPE_ID, PRICE, BRIEF, USERID, TIMES)
values (2, '2', '2', 1, 2, '2343444', 1, to_date('12-10-2012', 'dd-mm-yyyy'));
insert into PAY (ID, PAY_NAME, AUTHOR, TYPE_ID, PRICE, BRIEF, USERID, TIMES)
values (6, '6', '1', 0, 4000, '1', 1, to_date('12-08-2012', 'dd-mm-yyyy'));
insert into PAY (ID, PAY_NAME, AUTHOR, TYPE_ID, PRICE, BRIEF, USERID, TIMES)
values (5, '5', '1', 0, 1, '1', 1, to_date('12-10-2012', 'dd-mm-yyyy'));
insert into PAY (ID, PAY_NAME, AUTHOR, TYPE_ID, PRICE, BRIEF, USERID, TIMES)
values (4, '4', '1', 0, 100, '1', 1, to_date('12-09-2012', 'dd-mm-yyyy'));
insert into PAY (ID, PAY_NAME, AUTHOR, TYPE_ID, PRICE, BRIEF, USERID, TIMES)
values (7, '4', '1', 0, 566, '1', 1, to_date('03-03-2012', 'dd-mm-yyyy'));
insert into PAY (ID, PAY_NAME, AUTHOR, TYPE_ID, PRICE, BRIEF, USERID, TIMES)
values (11, '4', '1', 0, 566, '1', 1, to_date('03-04-2012', 'dd-mm-yyyy'));
insert into PAY (ID, PAY_NAME, AUTHOR, TYPE_ID, PRICE, BRIEF, USERID, TIMES)
values (10, '4', '1', 0, 566, '1', 1, to_date('03-05-2012', 'dd-mm-yyyy'));
insert into PAY (ID, PAY_NAME, AUTHOR, TYPE_ID, PRICE, BRIEF, USERID, TIMES)
values (9, '4', '1', 0, 566, '1', 1, to_date('03-06-2012', 'dd-mm-yyyy'));
insert into PAY (ID, PAY_NAME, AUTHOR, TYPE_ID, PRICE, BRIEF, USERID, TIMES)
values (8, '4', '1', 0, 566, '1', 1, to_date('03-07-2012', 'dd-mm-yyyy'));
commit;
3.统计sql(查询userid为1的用户2012年的每个月支出情况)
SELECT SUM(DECODE(EXTRACT(MONTH FROM B.TIMES), 1, B.PRICE, 0)) AS A,
SUM(DECODE(EXTRACT(MONTH FROM B.TIMES), 2, B.PRICE, 0)) AS B,
SUM(DECODE(EXTRACT(MONTH FROM B.TIMES), 3, B.PRICE, 0)) AS C,
SUM(DECODE(EXTRACT(MONTH FROM B.TIMES), 4, B.PRICE, 0)) AS D,
SUM(DECODE(EXTRACT(MONTH FROM B.TIMES), 5, B.PRICE, 0)) AS E,
SUM(DECODE(EXTRACT(MONTH FROM B.TIMES), 6, B.PRICE, 0)) AS F,
SUM(DECODE(EXTRACT(MONTH FROM B.TIMES), 7, B.PRICE, 0)) AS G,
SUM(DECODE(EXTRACT(MONTH FROM B.TIMES), 8, B.PRICE, 0)) AS H,
SUM(DECODE(EXTRACT(MONTH FROM B.TIMES), 9, B.PRICE, 0)) AS I,
SUM(DECODE(EXTRACT(MONTH FROM B.TIMES), 10, B.PRICE, 0)) AS J,
SUM(DECODE(EXTRACT(MONTH FROM B.TIMES), 11, B.PRICE, 0)) AS K,
SUM(DECODE(EXTRACT(MONTH FROM B.TIMES), 12, B.PRICE, 0)) AS L
FROM PAY B
WHERE USERID = 1
AND EXTRACT(YEAR FROM B.TIMES) = '2012'
4.统计结果如下
A B C D E F G H I J K L
0 0 566 566 566 566 566 4000 100 7 0 0
5.另外一种写法：对于时间的操作也可以用下面这个
SELECT SUM(DECODE(TO_CHAR(B.TIMES, 'MM'), '01', B.PRICE, 0)) M1,
SUM(DECODE(TO_CHAR(B.TIMES, 'MM'), '02', B.PRICE, 0)) M2,
SUM(DECODE(TO_CHAR(B.TIMES, 'MM'), '03', B.PRICE, 0)) M3,
SUM(DECODE(TO_CHAR(B.TIMES, 'MM'), '04', B.PRICE, 0)) M4,
SUM(DECODE(TO_CHAR(B.TIMES, 'MM'), '05', B.PRICE, 0)) M5,
SUM(DECODE(TO_CHAR(B.TIMES, 'MM'), '06', B.PRICE, 0)) M6,
SUM(DECODE(TO_CHAR(B.TIMES, 'MM'), '07', B.PRICE, 0)) M7,
SUM(DECODE(TO_CHAR(B.TIMES, 'MM'), '08', B.PRICE, 0)) M8,
SUM(DECODE(TO_CHAR(B.TIMES, 'MM'), '09', B.PRICE, 0)) M9,
SUM(DECODE(TO_CHAR(B.TIMES, 'MM'), '10', B.PRICE, 0)) M10,
SUM(DECODE(TO_CHAR(B.TIMES, 'MM'), '11', B.PRICE, 0)) M11,
SUM(DECODE(TO_CHAR(B.TIMES, 'MM'), '12', B.PRICE, 0)) M12
FROM PAY B
WHERE USERID = 1
AND TO_CHAR(B.TIMES, 'yyyy') = '2012'