期待どおりに機能するはずの長い道のりは次のとおりです。
SELECT
Employee.emp_Name,
'2011' AS `Year`,
'Dec' AS `Month`,
CASE (
IF(
DATE('1-12-2011') < DATE(Employee.Joining_Date)),
'0' --Not joined yet
IF (
(SELECT COUNT(*) FROM Holiday WHERE DATE('1-12-2011') = DATE(Holiday.date)) = 1,
'1', --National Holiday
IF (
(SELECT COUNT(*) FROM Leave WHERE DATE('1-12-2011') > DATE(Leave.to_Date) AND DATE('1-12-2011') < DATE(Leave.from_Date) AND Leave.Emp_Id = Employee.emp_id) = 1,
'2', --On Leave
IF(
(SELECT COUNT(*) FROM Doctor WHERE DATE('1-12-2011') > DATE(Doctor.Call_Date) AND Doctor.call_Done_By = Employee.emp_id) = 1 OR
(SELECT COUNT(*) FROM Chemist WHERE DATE('1-12-2011') > DATE(Chemist.Call_Date) AND Chemist.call_Done_By = Employee.emp_id) = 1,
'3' --Visit Doctor or Chemist
'4' --Employee was at work
)
)
)
)
)
WHEN 0 THEN 'N/A' --Not joined yet
WHEN 1 THEN 'L' --National Holiday
WHEN 2 THEN 'L' --On Leave
WHEN 3 THEN 'S' --Visit Doctor or Chemist
ELSE 'Y' --Employee was at work
END AS `1`, --first day of month
... AS `2`, --repeat for second day of the month till max day of current month replace '1-12-2011' with each different day of month
...
... AS `30`
FROM
Employee
私の提案は、コードの保守が容易になるように、各従業員のifステートメントを実行するビューを作成することです。これは疑似コードであり、実行するにはいくつかの変更が必要になる可能性があることに注意してください。
これがお役に立てば幸いです。