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我试图TotalTime null从表NewTimeAttendance... TotalTime数据类型执行具有值的记录nchar(10)

select * from newtimeattendance where TotalTime =  'NULL'

....没有

select * from newtimeattendance where TotalTime =  'null'

....没有

select * from newtimeattendance where TotalTime =  'Null'

....没有

select * from newtimeattendance where TotalTime =  null

....没有

select * from newtimeattendance where TotalTime =  Null

....没有

select * from newtimeattendance where TotalTime =  NULL

....没有

当我选择整个表格时,我可以看到有一些NULL TotalTime价值...... !!

这是小选择的声明..为什么不工作？有没有办法(特殊方式)用nchar类型执行'NULL' ？

提前致谢

我试图写一个声明中用于计算员工考勤和执行他们的id,name与天,他通过计算重复工作的前3个月id就NewTimeAttendance 为每月1,2和3.

我试过数:

Select COUNT(employeeid)
  from NewTimeAttendance
 where employeeid=1 and (month=1 or month = 2 or month = 3)

这绝对有效,但仅适用于一名员工.

第二次尝试:

SELECT COUNT(NewEmployee.EmployeeID)
  FROM NewEmployee INNER JOIN NewTimeAttendance 
    ON NewEmployee.EmployeeID = NewTimeAttendance.EmployeeID
   and (month=1 or month =2 or month = 3)

这是有效的,但它会计算所有员工,我希望它能够执行每个员工EmployeeId,EmployeeName并number of days作为新记录.

最后一次尝试:(在看到代码之前......这是错误的..但我正在尝试)

for i in  0..27 loop
   SELECT COUNT(NewEmployee.EmployeeID),NewEmployee.EmployeeId,EmployeeName
     FROM NewEmployee INNER JOIN NewTimeAttendance 
       ON NewEmployee.EmployeeID(i) = NewTimeAttendance.EmployeeID
      and (month=1 or month =2 or …