用于搜索日期的SQL查询

Question

I have written a SQL query which search the employee ATTENDANCE Table for the persons who are absent. But how can I show the dates I mean the date of the absent period? It works fine except the date. I want to show what's the day of that absent period? I am unable to show the date.

Sample:

BadgeNumber - EmployeeName - Absent Date
10042 - Mr. Erik - 2014-07-01

Code:

SELECT  SMEmployee.BadgeNumber,SMEmployee.EmployeeFullName,SMDepartment.DepartmentName
    FROM SMEmployee
    LEFT OUTER JOIN SMDepartment 
    ON SMDepartment.DepartmentID=SMEmployee.DepartmentID    
    WHERE EmployeeID NOT IN (
    SELECT empCheckInOut.USERID 
    FROM empCheckInOut 
    WHERE convert(date,CHECKTIME)='2014-07-01')

Answer 1

It seems that you capture the days employee is present in 'empCheckInOut' table.

You need to construct temp table with all the dates lets say of 1 month and then minus the dates that are captured in 'empCheckInOut' table.

eg #temp will have 06-01-2014, 06-02-2014, 06-03-2014, ... (all 30 days of Jun)

CheckInOut will have 06-01-2014, 06-03-2014,... (emp is absent on 2nd Jun, so total 29 days of Jun captured here)

Then, subtract one from the other and you will get dates when employee is absent.

Answer 2

Normally to check for the lack of existence of a record (as you are doing here for attendence, checking the employee did not check in / out on a day) it is more efficient to use a LEFT OUTER JOIN and the check for NULL in one of the fields in the WHERE clause (ie, a LEFT JOIN where no row found).

However this also won't give you the date.

I presume that you want to check a selection of dates, and this need to pull through the date they were absent.

As such maybe use a series of unioned simple queries to get the dates, CROSS JOIN that to your employee table and LEFT JOIN it to the empCheckInOut table. This way you can put out the date.

SELECT  SMEmployee.BadgeNumber,SMEmployee.EmployeeFullName,SMDepartment.DepartmentName, subDate.aDate
FROM SMEmployee
CROSS JOIN (SELECT '2014-07-01' AS aDate UNION SELECT '2014-06-30') subDate
LEFT OUTER JOIN SMDepartment 
ON SMDepartment.DepartmentID=SMEmployee.DepartmentID    
LEFT OUTER JOIN empCheckInOut
ON SMEmployee.EmployeeID = empCheckInOut.USERID 
AND convert(date,CHECKTIME) = subDate.aDate
WHERE empCheckInOut.USERID IS NULL