CREATE TABLE TX(
A varchar2(50),
B varchar2(50),
C Nvarchar2(50),
D number(10)
);

INSERT INTO TX (A,B,C,D)
VALUES ('2021/2/1','adidas','鞋子',325);
INSERT INTO TX (A,B,C,D)
VALUES ('2021/4/1','adidas','鞋子',325);
INSERT INTO TX (A,B,C,D)
VALUES ('2021/5/1','adidas','鞋子',316);
INSERT INTO TX (A,B,C,D)
VALUES ('2021/7/1','adidas','鞋子',325);
INSERT INTO TX (A,B,C,D)
VALUES ('2021/7/1','nike','鞋子',325);

CREATE TABLE TY(
A varchar2(50));

INSERT INTO TY (A)
VALUES ('2021/1/1');
INSERT INTO TY (A)
VALUES ('2021/2/1');
INSERT INTO TY (A)
VALUES ('2021/3/1');
INSERT INTO TY (A)
VALUES ('2021/4/1');
INSERT INTO TY (A)
VALUES ('2021/5/1');
INSERT INTO TY (A)
VALUES ('2021/6/1');
INSERT INTO TY (A)
VALUES ('2021/7/1');

SELECT TY.A,
LAST_VALUE(TX.B IGNORE NULLS) OVER (ORDER BY TY.A,TX.B,TX.C) AS B,
LAST_VALUE(TX.C IGNORE NULLS) OVER (ORDER BY TY.A,TX.B,TX.C) AS C,
LAST_VALUE(TX.D IGNORE NULLS) OVER (ORDER BY TY.A,TX.B,TX.C) AS D
FROM TY
LEFT JOIN TX ON TX.A=TY.A
ORDER BY TY.A,TX.B,TX.C

Demo

Oracle 不太熟~
MSSQL的話~我是想到這方式@@..

declare @Tab table(
	日期 date
	,廠商 nvarchar(50)
	,物品 nvarchar(50)
	,金額 int
)

insert into @Tab
values('2021/2/1','adidas','鞋子','325')
,('2021/4/1','adidas','鞋子','325')
,('2021/5/1','adidas','鞋子','316')
,('2021/7/1','adidas','鞋子','325')
,('2021/7/1','nike','鞋子','325')

declare @TmpDate table(
	日期 date
)

insert into @TmpDate
values('2021/2/1')
,('2021/3/1')
,('2021/4/1')
,('2021/5/1')
,('2021/6/1')
,('2021/7/1')

select 設定日
,(
	case when 資料日 is null
	then (
		select top 1 廠商
		from @Tab c
		where 廠商 = 廠商
		and c.日期 < 設定日
		order by c.日期 desc
	)
	else 廠商
	end
) 廠商
,(
	case when 資料日 is null
	then (
		select top 1 物品
		from @Tab c
		where 廠商 = 廠商
		and c.日期 < 設定日
		order by c.日期 desc
	)
	else 物品
	end
) 物品
,(
	case when 資料日 is null
	then (
		select top 1 金額
		from @Tab c
		where 廠商 = 廠商
		and c.日期 < 設定日
		order by c.日期 desc
	)
	else 金額
	end
) 金額
from (
	select a.日期 設定日
	,b.日期 資料日
	,廠商
	,物品
	,金額
	from @TmpDate a
	left join @Tab b on a.日期 = b.日期
) k

你的 last_value 沒問題. 問題一出在資料庫無法判斷每個商品該出時間與次數. 換句話說, 你先產生完整的表格再讓資料庫作填充題.

簡易做法:

1. 準備資料

drop table sales;
CREATE TABLE sales(
edate date,
ebrand varchar2(20),
eproduct varchar2(20),
eamount number
);

INSERT INTO sales 
VALUES (to_date('2021/2/1','YYYY/MM/DD'),'adidas','shoe',325);
INSERT INTO sales
VALUES (to_date('2021/4/1','YYYY/MM/DD'),'adidas','shoe',315);
INSERT INTO sales
VALUES (to_date('2021/5/1','YYYY/MM/DD'),'adidas','shoe',316);
INSERT INTO sales
VALUES (to_date('2021/9/1','YYYY/MM/DD'),'adidas','shoe',456);
INSERT INTO sales
VALUES (to_date('2021/2/1','YYYY/MM/DD'),'nike','shoe',325);
INSERT INTO sales
VALUES (to_date('2021/8/1','YYYY/MM/DD'),'nike','shoe',123);
commit;

2. 準備要填空的完整版

with xx as (
select add_months(to_date('01/01/2021','MM/DD/YYYY'),level) edate from dual connect by level<10
), yy as (
select 'adidas' ebrand from dual
union all
select 'nike' ebrand from dual
), zz as (
select 'shoe' eproduct from dual
)
select *
from xx,yy,zz
order by 2,3,1;

3. 合體

select * from sales;

with xx as (
select add_months(to_date('01/01/2021','MM/DD/YYYY'),level) edate from dual connect by level<10
), yy as (
select 'adidas' ebrand from dual
union all
select 'nike' ebrand from dual
), zz as (
select 'shoe' eproduct from dual
), kkk as (
select *
from xx,yy,zz
)
select kkk.*,sales.*
,last_value(sales.eamount ignore nulls) over (partition by kkk.ebrand,kkk.eproduct order by kkk.edate rows between unbounded preceding and current row) yy
from kkk
left join sales on kkk.edate=sales.edate and kkk.ebrand=sales.ebrand and kkk.eproduct=sales.eproduct
order by 2,3,1;

成品:

當然你準備填空的表格可以更華麗一點. 上面的範例假設時間, 品牌與產品都一樣要填空. 你可以繼續客製化. (不過我假設你這個大慨率是要給 BI 做表格/圖表的, 所以應該是屬於可直接服用狀態)