SQL Server 2022

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CREATE TABLE employees 
(
    Employee_ID	INT,
    Department_ID	INT,
    Start_Date	DATE,
    End_Date	DATE
);

INSERT INTO employees (Employee_ID, Department_ID, Start_Date, End_Date) VALUES
  ('395961', '0001', '2022-01-01', '2022-03-31'),
  ('395961', '0002', '2022-01-01', '2022-01-31'),
  ('395961', '0001', '2022-06-01', '2022-10-31'),
  ('395961', '0001', '2022-11-01', '2022-12-31'),
  ('395962', '0001', '2022-01-01', '2022-03-31'),
  ('395962', '0002', '2022-01-01', '2022-01-31'),
  ('395962', '0002', '2022-02-01', '2022-04-30'),
  ('395962', '0001', '2022-06-01', '2022-10-31'),
  ('395962', '0001', '2022-11-01', '2022-12-31'),
  ('395963', '0001', '2022-01-01', '2022-05-31'),
  ('395963', '0002', '2022-06-01', '2022-12-31');
11 rows affected

DECLARE @Start_Date DATE, @End_Date DATE;

SET @Start_Date = '2022-01-01';
SET @End_Date = '2022-12-31';

WITH cal (date) AS (
  SELECT @Start_Date
  UNION ALL
  SELECT DATEADD(day, 1, date)
  FROM cal
  WHERE date < @End_Date
)
SELECT e.Employee_ID, COUNT(cal.date) AS Days_Not_Hired
FROM cal
CROSS JOIN (SELECT DISTINCT Employee_ID FROM employees) e
LEFT JOIN employees e2
  ON cal.date BETWEEN e2.Start_Date AND e2.End_Date
  AND e.Employee_ID = e2.Employee_ID
WHERE e2.Employee_ID IS NULL
GROUP BY e.Employee_ID
OPTION(MAXRECURSION 365);


Employee_ID
Days_Not_Hired


395961
61

395962
31


WITH cal (date) AS (
  SELECT CAST('2022-01-01' AS DATE)
  UNION ALL
  SELECT DATEADD(day, 1, date)
  FROM cal
  WHERE date < '2022-12-31'
)
SELECT e.Employee_ID, COUNT(cal.date) AS Days_Not_Hired
FROM cal
CROSS JOIN (SELECT DISTINCT Employee_ID FROM employees) e
LEFT JOIN employees e2
  ON cal.date BETWEEN e2.Start_Date AND e2.End_Date
  AND e.Employee_ID = e2.Employee_ID
WHERE e2.Employee_ID IS NULL
GROUP BY e.Employee_ID
OPTION(MAXRECURSION 365);


Employee_ID
Days_Not_Hired


395961
61

395962
31