SQL query to return aggregations in a constant format, even when the categories are missing - sql

Question

Is it possible with SQL Server to return table with a constant format?
Let's say we have the following raw data:
DATE | CATEGORY | VALUE
---------------------------------
01.01.2022 | Category 1 | 10
01.01.2022 | Category 1 | 20
01.01.2022 | Category 1 | 33
01.01.2022 | Category 3 | 15
03.01.2022 | Category 1 | 10
03.01.2022 | Category 2 | 20
03.01.2022 | Category 3 | 50
(...)
And the desired output would be:
DATE | CATEGORY | VALUE
---------------------------------
01.01.2022 | Category 1 | 63
01.01.2022 | Category 2 | 0
01.01.2022 | Category 3 | 15
02.01.2022 | Category 1 | 0
02.01.2022 | Category 2 | 0
02.01.2022 | Category 3 | 0
03.01.2022 | Category 1 | 10
03.01.2022 | Category 2 | 20
03.01.2022 | Category 3 | 50
(...)
Please notice that in the desired outcome there's a date present that's missing in the raw data, as well as sum of VALUE are 0 when the category is not present for a given date in the raw data.

Answer 1

-- Contiguous dates table
DECLARE #dates TABLE(dt date) ;
DECLARE #dateFrom date;
DECLARE #dateTo date;
select #dateFrom = (Select DateAdd(day, -1, Min(date)) from Agg);
select #dateTo = (Select Max(date) from Agg);
-- Query:
WHILE(#dateFrom < #dateTo)
BEGIN
SELECT #dateFrom = DATEADD(day, 1,#dateFrom)
INSERT INTO #dates
SELECT #dateFrom
END
-- Category table
DECLARE #categories TABLE(category nvarchar(20)) ;
insert into #categories values ('Category 1'),('Category 2'),('Category 3');
-- This cte helps in creating the constant output required
with cte1 as (
select dt, category from
#dates cross join #categories
)
select cte1.dt as [Date], cte1.category, Sum(coalesce(yourTableName.value,0)) as Value
from cte1 left join yourTableName
on cte1.dt = yourTableName.[Date] and cte1.category = yourTableName.category
group by cte1.dt, cte1.category
order by cte1.dt, cte1.category

Answer 2

WITH ctedate AS
(
SELECT d= v2.d * 10 + v1.d
FROM (VALUES (0), (1), (2), (3), (4), (5), (6), (7), (8), (9)) v1(d)
CROSS JOIN (VALUES (0), (1), (2), (3), (4), (5), (6), (7), (8), (9)) v2(d)
)
Select b.date, a.category, sum(coalesce(a.value,0)) from
yourtablename a
cross join
(SELECT DATEADD(DAY, ctedate.d, '2022-01-01') date
FROM ctedate
ORDER BY ctedate.d) b
group by b.date, a.category

Answer 3

Here is a script with solution using cte:
Calculate the min date and the max date
then make a calendar (cte1) with all dates between (min date) and (max date) using recursivity
get the list of all category => cte2
make a cross join between cte1 and cte2 ==> cte3
make a left join between cte3 and the table data (#mytable), replace Null values by 0
declare #mytable as table (date date,category varchar(50),Value int)
insert into #mytable values
('01/01/2022','Category 1',10),
('01/01/2022','Category 1',20),
('01/01/2022','Category 1',33),
('01/01/2022','Category 3',15),
('01/03/2022','Category 1',10),
('01/03/2022','Category 2',20),
('01/03/2022','Category 3',50);
declare #mindate as date, #maxdate as date
select #mindate=min(date),#maxdate=max(date) from #mytable;
with
cte1 as (select #mindate mydate union all select dateadd(day,1,mydate) from cte1 where dateadd(day,1,mydate) <= #maxdate),
cte2 as (select distinct(category) from #mytable),
cte3 as (select mydate,category from cte1 cross join cte2),
cte4 as (select mydate date ,cte3.category,isnull(value,0) value from cte3 left outer join #mytable t on cte3.mydate=t.date and cte3.category=t.category )
select * from cte4