使用場景:統計支出表中某人某年的每個月的支出情況
1.建立表如下（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, --金額
brief varchar2(1000),
userid number(11), --使用者id
times date, --時間
primary key(id)
)2.插入測試資料
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.統計sql(查詢userid為1的使用者2023年的每個月支出情況)
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.統計結果如下
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.另外一種寫法：對於時間的操作也可以用下面這個
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'
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