Displaying student absent dates - sql

Question

Here is the table I want to display:
tblAttendance table
CustomerId
Id
Attendence
Date
and
tblStudent
CustomerId
Name
Now I want to search by from to date and want absent date.
How can I achieve this?
I tried below code:
ALTER PROCEDURE spExceptDate
AS
declare #StartDate DATE, #EndDate DATE
set #StartDate = '2020-02-15';
set #EndDate = '2020-02-25';
BEGIN
SELECT CustomerId,FirstName+' '+LastName,Date,Attendance
FROM
[dbo].[tblAttendance] att
LEFT JOIN
[dbo].[tblStudent] st
ON att.CustomerId = st.Code
EXCEPT
SELECT CustomerId,FirstName+' '+LastName,Date,Attendance
FROM
[dbo].[tblAttendance] att
LEFT JOIN
[dbo].[tblStudent] st
ON att.CustomerId = st.Code
where att.Date>='2020-02-15' and att.Date<='2020-02-25'
END
GO
i want date for which student absend

Answer 1

Basically what you need is list of possible dates between From and To
DECLARE #StartDate DATE = '2020-02-15',
#EndDate DATE = '2020-02-25' ;
--Create a CTE to get all dates between from and to (you should filter holidays and weekends)
WITH SchoolCalendar (WorkingDay)
AS (SELECT #StartDate
UNION ALL
SELECT DATEADD(DAY, 1, WorkingDay)
FROM SchoolCalendar
WHERE WorkingDay< #EndDate
)
--Use the CTE to determine the Absense records
SELECT st.Code CustomerId, st.FirstName+' '+st.LastName Name,st.WorkingDay Date, COALESCE(Attendance,'A') Attendance
FROM (SELECT * from SchoolCalendar, tblStudent) st
LEFT JOIN [dbo].[tblAttendance] att ON att.Date = st.WorkingDay AND att.CustomerId = st.Code
WHERE st.WorkingDay>=#StartDate and st.WorkingDay<=#EndDate
ORDER BY st.Code, st.WorkingDay

Answer 2

You may need only one query if you want to fetch only absent student names from the given date range
SELECT CustomerId,FirstName+' '+LastName,Date,Attendance
FROM [dbo].[tblAttendance] att
LEFT JOIN [dbo].[tblStudent] st ON att.CustomerId = st.Code
WHERE att.Date>='2020-02-15' and att.Date<='2020-02-25' AND att.Attendance <> 'P'
^^^^^^^^^^^^^^^^^^^^