T SQL, Get new customer added or deleted from historical table

Question

I have a Table containing historical data. Every day the same staff list will be added with the new dates (between 1200-12500 staff each day however only a few staff might be newly added todaysDate or they may have left the company yesterday and not showing on todays list).

I want to know each day which staff wasn't on yesterday list, it is new staff and the staff was showing yesterday but not today because they left company. I have tried the following but no joy please help my historical table is like below and I need a script to get the rows for ID4 and ID5 only.

StaffID	StaffName	CensusDate
ID1	Staff1	02/03/2021
ID1	Staff1	03/03/2021
ID2	Staff2	02/03/2021
ID2	Staff2	03/03/2021
ID3	Staff3	02/03/2021
ID3	Staff3	03/03/2021
ID4	Staff4	02/03/2021	not showing today
ID5	Staff5	03/03/2021	is newly added today
ID6	Staff6	02/03/2021
ID6	Staff6	03/03/2021
ID7	Staff7	02/03/2021
ID7	Staff7	03/03/2021

SELECT StaffID, StaffNAME, CensusDate
FROM table1 AS A 
LEFT JOIN table1 AS B 

ON A.StaffID = B.StaffID AND A.date = GETDATE())  AS date) 
and B.date = CAST(DATEADD(day, -1, convert(date, GETDATE())) AS date) 
AND A.staffID IS NULL

Answer 1

There's likely a simpler way, but I think this achieves what you're looking for:

WITH CTE_TodaysStaff AS
(
    SELECT DISTINCT T1.StaffID
    FROM table1 AS T1
    WHERE T1.CensusDate = CAST(GETDATE() AS DATE)
),
CTE_NotShowingToday AS
(
    SELECT DISTINCT T1.StaffID
    FROM table1 AS T1
    LEFT JOIN CTE_TodaysStaff AS T2
         ON T1.StaffID = T2.StaffID
    WHERE T1.CensusDate = CAST(DATEADD(DAY, -1, GETDATE()) AS DATE)
        AND T2.StaffID IS NULL
 ),
CTE_NewToday AS
(
    SELECT DISTINCT T1.StaffID
    FROM CTE_TodaysStaff AS T1
    LEFT JOIN table1 AS T2
        ON T1.StaffID = T2.StaffID
        AND T2.CensusDate < CAST(GETDATE() AS DATE)
    WHERE T2.StaffID IS NULL
 )

 SELECT T1.StaffID, T1.StaffNAME, T1.CensusDate, 
     CAST(CASE WHEN T2.StaffID IS NULL THEN 0 ELSE 1 END AS BIT) AS IsNotShowingToday,
     CAST(CASE WHEN T3.StaffID IS NULL THEN 0 ELSE 1 END AS BIT) AS IsNewToday
FROM table1 AS T1
LEFT JOIN CTE_NotShowingToday AS T2
    ON T1.StaffID = T2.StaffID
LEFT JOIN CTE_NewToday AS T3
    ON T1.StaffID = T3.StaffID

Answer 2

Not sure I completely understand your intention or the difference between Table1 and Table2. If you are trying to find just the IDs that only occur once in the last two days.

SELECT StaffID, count(StaffID)
FROM Table1 
WHERE CensusDate >= cast(dateadd(day, -2, getdate()) as date)
Group By StaffID