Can I "left join" days between 2 dates in sql server? - sql-server

Question

There is a table in SQL Server where data is entered day by day. In this table, data is not filled in some days.
Therefore, there are no records in the table.
Sample: dataTable
I need to generate a report like the one below from this table.
Create a table with all the days of the year. I know that I can output a report by "joining" the "dataTable" table.
But this solution seems a bit strange to me.
Is there another way?
the code i use for temp date table
CREATE TABLE tempDate (
calendarDate date,
PRIMARY KEY (calendarDate)
)
DECLARE
#start DATE= '2021-01-01',
#dateCount INT= 730,
#rowNumber INT=1
WHILE (#rowNumber < #dateCount)
BEGIN
INSERT INTO tempDate values (DATEADD(DAY, #rowNumber, #start))
set #rowNumber=#rowNumber+1
END
GO
select * from tempDate
This is how I join using this table
SELECT
*
FROM
tempDate td WITH (NOLOCK)
LEFT JOIN dataTable dt WITH (NOLOCK) ON dt.reportDate = td.calendarDate
WHERE
td.calendarDate BETWEEN '2021-09-05' AND '2021-09-15'

Answer 1

Create a table with all the days of the year. I know that I can output a report by "joining" the "dataTable" table.
This is the way. You can generate that "table" on the fly if you really want to, but normally the best way is to simply have a calendar table.

Answer 2

You can use common expression tables for dates. The code you need:
IF(OBJECT_ID('tempdb..#t') IS NOT NULL)
BEGIN
DROP TABLE #t
END
CREATE TABLE #t
(
id int,
dt date,
dsc varchar(100),
)
INSERT INTO #t
VALUES
(1, '2021.09.08', 'a'),
(1, '2021.09.09', 'b'),
(1, '2021.09.12', 'c')
DECLARE #minDate AS DATE
SET #minDate = (SELECT MIN(dt) FROM #t)
DECLARE #maxDate AS DATE
SET #maxDate = (SELECT MAX(dt) FROM #t)
;WITH cte
AS
(
SELECT #minDate AS [dt]
UNION ALL
SELECT DATEADD(DAY, 1, [dt])
FROM cte
WHERE DATEADD(DAY, 1, [dt])<=#maxDate
)
SELECT
ISNULL(CAST(t.id AS VARCHAR(10)), '') AS [id],
cte.dt AS [dt],
ISNULL(t.dsc, 'No record has been entered in the table.') AS [dsc]
FROM
cte
LEFT JOIN #t t on t.dt=cte.dt

Answer 3

The fastest method is to use a numbers table, you can get a date list between 2 dates with that:
DECLARE #Date1 DATE, #Date2 DATE
SET #Date1 = '20200528'
SET #Date2 = '20200625'
SELECT DATEADD(DAY,number+1,#Date1) [Date]
FROM master..spt_values
WHERE type = 'P'
AND DATEADD(DAY,number+1,#Date1) < #Date2
If you go go in LEFT JOIN this select, whit your table, you have the result that you want.
SELECT *
FROM (SELECT DATEADD(DAY,number+1,#Date1) [Date]
FROM master..spt_values WITH (NOLOCK)
WHERE type = 'P'
AND DATEADD(DAY,number+1,#Date1) < #Date2 ) as a
LEFT JOIN yourTable dt WITH (NOLOCK) ON a.date = dt.reportDate
WHERE td.[Date] BETWEEN '2021-09-05' AND '2021-09-15'