Sql server SQL Server T-SQL：根据优先级值startdate和enddate获取记录集

我在做一个考勤系统。我必须填写以下表格：

计划：包含名称nvarchar字段以及开始和结束日期时间字段。 策略：也包含开始和结束日期时间字段。 PolicySchedule交叉表：在外键旁边包含优先级int字段。 End datetime字段可为空，表示开放期间

最高优先级的计划将在其时间和策略时间内应用和激活

我需要获得每个策略中应用的计划列表，以及它们的激活周期开始和结束时间，知道计划可能是交叉的。这里不涉及政策

例如：

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获取请求结果的最有效方法是什么？

假设您使用的是SQL Server 2005或更高版本，您可以使用外部应用程序来查找具有最高优先级的策略：

select  *
from    Schedule s
outer apply
        (
        select  top 1 *
        from    PolicySchedule ps
        join    Policy p
        on      p.id = ps.policyid
        where   s.StartTime <= p.EndTime
                and p.StartTime <= s.EndTime
        order by
                ps.priority desc
        ) pol

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如果有必须重叠的时间段，您可以在外部应用中添加where子句。

如果您有许多单独的策略和计划，但每个策略的计划很少，最简单的方法将非常有效：

WITH    dates (policyId, changeDate) AS
        (
        SELECT  policyId, changeDate,
                ROW_NUMBER() OVER (PARTITION BY policyId ORDER BY changeDate) AS rn
        FROM    (
                SELECT  policyId, startDate AS changeDate
                FROM    policySchedule ps
                JOIN    schedule s
                ON      s.id = ps.scheduleId
                UNION
                SELECT  policyId, endDate AS changeDate
                FROM    policySchedule ps
                JOIN    schedule s
                ON      s.id = ps.scheduleId
                ) q
        ),
        ranges (startDate, endDate)AS
        (
        SELECT  d1.policyId,
                d1.changeDate,
                d2.changeDate
        FROM    dates d1
        JOIN    dates d2
        ON      d2.policyId = d1.policyId
                AND d2.rn = d1.rn + 1
        )
SELECT  *
FROM    policy p
JOIN    ranges r
ON      r.policyId = p.id
CROSS APPLY
        (
        SELECT  TOP 1 s.*
        FROM    policySchedules ps
        JOIN    schedule s
        ON      ps.policyId = p.id
                AND s.id = ps.scheduleId
        WHERE   ps.startDate BETWEEN r.startDate AND r.endDate
                AND ps.endDate BETWEEN r.startDate AND r.endDate
        ORDER BY
                ps.Priority DESC
        )

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开始时间和结束时间在策略上也可以相交吗？@Quassnoi:不，策略是独立的。我需要每个策略的结果集。这不考虑策略的生效日期。如果我正确，这将返回每个计划的最高优先级策略。我真正想要的是每个策略的应用/活动计划部分。。。

WITH    dates (policyId, changeDate) AS
        (
        SELECT  policyId, changeDate,
                ROW_NUMBER() OVER (PARTITION BY policyId ORDER BY changeDate) AS rn
        FROM    (
                SELECT  policyId, startDate AS changeDate
                FROM    policySchedule ps
                JOIN    schedule s
                ON      s.id = ps.scheduleId
                UNION
                SELECT  policyId, endDate AS changeDate
                FROM    policySchedule ps
                JOIN    schedule s
                ON      s.id = ps.scheduleId
                ) q
        ),
        ranges (startDate, endDate)AS
        (
        SELECT  d1.policyId,
                d1.changeDate,
                d2.changeDate
        FROM    dates d1
        JOIN    dates d2
        ON      d2.policyId = d1.policyId
                AND d2.rn = d1.rn + 1
        )
SELECT  *
FROM    policy p
JOIN    ranges r
ON      r.policyId = p.id
CROSS APPLY
        (
        SELECT  TOP 1 s.*
        FROM    policySchedules ps
        JOIN    schedule s
        ON      ps.policyId = p.id
                AND s.id = ps.scheduleId
        WHERE   ps.startDate BETWEEN r.startDate AND r.endDate
                AND ps.endDate BETWEEN r.startDate AND r.endDate
        ORDER BY
                ps.Priority DESC
        )