MS Access查询需要很长时间才能执行

Question

我使用以下简单查询，执行时间超过一分钟。 有人会帮助我吗

SELECT qryCredit_Points.Employee_ID, qryCredit_Points.First_Name,
qryCredit_Points.Last_Name, Sum(qryCredit_Points.TotalCredit) AS   
SumOfTotalCredit

FROM (  
SELECT emp.*, 
          (SELECT top 1 a.attend_date 
           FROM Attendance AS a 
           WHERE a.ID_Employee=at.ID_Employee and a.attend_date > at.attend_date 
           order by a.attend_date asc ) 
           AS NextDate, 
           IIf(IsNull(NextDate),Now(),Nextdate) AS next123, 
           Next123-at.attend_date AS difference, at.attend_date, 
           IIf(at.attend_date+90<Next123,1,0) AS Day90Credit, 
           IIf(at.attend_date+90<Next123,at.attend_date+90,at.attend_date+365) AS CreditDate, 
           IIf((Day90Credit=0 And CreditDate<Now()) Or Day90Credit=1,1,0) AS TotalCredit 
           FROM attendance AS [at], 
           Employees AS emp WHERE (((emp.Employee_ID)=[at].[ID_Employee])) 
) AS qryCredit_Points

GROUP BY qryCredit_Points.Employee_ID, qryCredit_Points.First_Name, 
qryCredit_Points.Last_Name;;