Question

我有两张桌子：员工和约会。

1员工可以有多个约会。有一个字段：可见性可以容纳0,1或2.

  0: show any of the appointment, 
  1: Show this appointment only, 
  2: Don't show the appointment.

现在我想选择员工和约会的记录：

如果可见性为1，则选择该记录而不是任何其他记录
如果可见性为0，则只选择一条记录，例如前1条
如果可见性为2，则为该记录选择空值，但员工ID除外。

有人能指出我如何使用Sql Server 2000完成它吗？

Answer 1

With SelectedAppointments AS
{
   SELECT * FROM Appointments WHERE Visibility <> 2 
}

SELECT  Employee.Id, < All columns of SelectedAppointments unless EmployeeId> 
   FROM Employee LEFT JOIN SelectedAppointments   
   on Employee.Id = SelectedAppointments.EmployeeId

Answer 2

select *
from Employee as Emp
  left outer join
    (select top 1 *
     from Appointments
     where Visibility <> 2
     order by Visibility desc) as App
  on Emp.EmpID = App.EmpID

Answer 3

我做了几个假设。

可能有多个约会
如果你有1和0的约会，你想保证显示的是<1>。

您只能拥有1条

的记录

SELECT
    e.empid,
    COALESCE(OneAppoint.appointmentID, ZeroAppoint.appointmentID) appointmentID
FROM
    employee e
    LEFT JOIN appointment ZeroAppoint
        INNER JOIN (
        SELECT
            max(a.appointmentid) appointmentid ,
        a.EmpID    
        FROM
            appointment a
        WHERE
            a.Visibility =0 

            ) maxZeroAppoint
        ON ZeroAppoint.appointmentid = maxZeroAppoint.appointmentid
    ON e.empID = ZeroAppoint.empID
    LEFT JOIN appointment OneAppoint
    ON e.empID = OneAppoint.empID 
        and OneAppoint.Visibility = 1

根据字段值选择行

3 个答案: