我需要设计数据库结构来邮件报告调度。到目前为止，我提出这个设计如下：
**ReportSchedule**
- ScheduleId
- ReportName
- Subject
- To
- UserId
- Body
- Remarks
**ScheduleDaily**
- Id
- ScheduleId
- StartDate
- EndDate
- SendTime
**ScheduleWeekly**
- Id
- ScheduleId
- StartDate
- EndDate
- SendTime
- DayOfWeek
**ScheduleMonthly**
- Id
- ScheduleId
- StartDate
- EndDate
- SendTime
- MonthOfYear
- DayOfWeek
..................
我对这个设计不满意，我需要一个涵盖所有参数的表（可能包括递归规则）。请推荐！！
As a first step, I see that most of the columns in the Schedule* tables are common. So you could move them in a ScheduleCommon table. But leave an id column behind, which will be the PK of the remaining tables and a FK to the ScheduleCommon table at the same time. That makes it an IS-A relation.
The above step will actually add an extra table to your schema, but IMHO it's a necessary normalization step.
I'm thinking, you could replace the recurring rules in your tables with an EveryHours field and a LastRun one. That way you can determine if LastRun+EveryHours has come to past, and the job needs to run again (and update the LastRun field).
The above will eliminate the Schedule* tables, since those fields are common and can be moved to the ScheduleCommon table. That leaves you with only two tables.
Provided that each report schedule has only one recurring schedule, the relation of the two tables becomes 1:1 and the one can absorb the other. But I don't think this is the case. Let's examine the example you provided in the comments: "send mail every Monday,Tuesday at 3:00PM of the month January". That's not one schedule but actually two:
ScheduleId StartDate EndDate EveryHours
ABC 2014-01-06 3:00PM 2014-02-01 3:00PM 192
ABC 2014-01-07 3:00PM 2014-02-01 3:00PM 192
As you can see, you will have to maintain multiple schedules for the same task, which makes the relation 1:N.