0

我有这个问题：下一个预定的重复约会的客户列表，即每年、每月或每季度。

我拥有的表\列是：

customer
   customer_ID
service
   customer_ID
   service_RecID
Resource
   service_RecID
   Recurrence_RecID
   Date_Time_Start
Recurrence
   Recurrence_RecID
   RecurType
   RecurInterval
   DaysOfWeek
   AbsDayNbr
   SelectInterval

它被建模为在设置日程时，date_start_time 是第一次重复约会发生的日期。前任。

Recurrence_RecID = 10
RecurType = m (could be y, or d as well for yearly or daily)
RecurInterval = 6 (if recurType = y, this would mean every 6 years)

鉴于系统每晚生成这些，我将如何编写查询来计算每个客户的下一个预定约会？我最初想使用 Resource.Date_Time_Start 并循环直到变量 nextAppointment >= today()，但是在 SQL 中运行循环是一种好习惯吗？

如果需要更多信息，请告诉我。非常感谢！

编辑：我会做一个 sqlfiddle。

4

1 回答 1

1

我建议使用子查询而不是循环。这样更有效率。这可能不准确，但类似于...

SELECT 
    *
FROM
(      
SELECT
    customer.customer_id,
    service.service_RecID,
    Resource.Date_Time_Start,
    Recurrence.Recurrence_RecID,
    RecurType,
    RecurInterval,
    DaysOfWeek,
    AbsDayNbr,
    SelectInterval,
    NextAppointmentDate=
    CASE 
        WHEN RecurType='m' THEN DATEADD(MONTH,RecurInterval,Resource.Date_Time_Start)
        WHEN RecurType='y' THEN DATEADD(YEAR,RecurInterval,Resource.Date_Time_Start)
    ELSE 
        NULL
    END        
FROM
    Recurrence
    INNER JOIN Resource ON Resource.Recurrence_RecID=Recurrence.Recurrence_RecID
    INNER JOIN service ON service.service_RecID=Resource.service_RecID
    INNER JOIN customer ON customer.customer_ID=service.customerID
)AS X
WHERE
    NextAppointmentDate>=GETDATE()
ORDER BY Fields...
于 2013-02-08T02:39:07.467 回答