SQL获取在给定时间间隔内连续X天可用的ID

在SQL表中，我使用StartDate/EndDate列保留各种资源的预订：

ResourceID,  StartDate,   EndDate
-----------------------------------
1          2009-01-01    2009-01-05
1          2009-01-07    2009-01-10
2          2009-01-03    2009-01-18

我需要生成一个列表，列出给定时间间隔内至少连续X天可用的所有资源：即从2009-01-01到2009-01-20，X=5个连续天

例如，对于ResourceID=1，最大可用时间间隔为2009-01-10=>2009-01-20，因此这符合条件，但对于ResourceID=2，没有5天的可用时间间隔。有一个是2009-01-01=>2009-01-03，另一个是2009-01-18=>2009-01-20，都不够长

编辑：

根据Quassnoi的回答，我添加了一些修改来处理一些边缘情况：资源不带保留，或者保留跨越整个查找周期

这看起来像是最终结果。谢谢你的帮助

WITH   avRows AS        (         
     SELECT  a.ID as aid,startDate , endDate , ROW_NUMBER() OVER (PARTITION BY ResourceID ORDER BY endDate ) AS rn   
     FROM    tblResources a left outer join tblReservations  b          
     on b.ResourceID = a.ID and (startDate  BETWEEN '2009-01-01' AND '2009-01-20'  OR endDate  BETWEEN '2009-01-01' AND '2009-01-20' )
     where a.ID NOT IN (select distinct ResourceID from tblReservations where    (startDate  <'2009-01-01'   AND  endDate  > '2009-01-20' ))
     )SELECT  DISTINCT COALESCE(rs.aid, rp.aid)

      FROM   avRows rs FULL JOIN    avRows rp ON   rs.aid = rp.aid  AND rp.rn = rs.rn - 1 
      WHERE   DATEDIFF(day, COALESCE(rp.endDate , '2009-01-01'), COALESCE(rs.startDate , '2009-01-20')) >= 5

更新2：

更详细的解释和性能测试：

适用于SQL Server、Oracle和PostgreSQL 8.4 在MySQL中工作

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你需要知道具体的日期吗，还是只有一个可用的日期？只是一个间隔是可用的。不管是有多个间隔还是什么时候，它都能工作！我知道有个“吻你”的按钮。把我从痛苦的夜晚救了出来

SELECT  resourceID
FROM    mytable
WHERE   startDate BETWEEN '2009-01-01' AND '2009-01-20'
        AND DATEDIFF(day, CASE WHEN endDate < '2009-01-20' THEN endDate ELSE '2009-01-20' END, startDate) >= 5
UNION
SELECT  resourceID
FROM    mytable
WHERE   endDate BETWEEN '2009-01-01' AND '2009-01-20'
        AND DATEDIFF(day, endDate, CASE WHEN startDate > '2009-01-01' THEN startDate ELSE '2009-01-01' END) >= 5

WITH    rows AS
        (
        SELECT  ResourceID, StartDate, EndDate, ROW_NUMBER() OVER (PARTITION BY ResourceID ORDER BY EndDate) AS rn
        FROM    mytable
        WHERE   StartDate BETWEEN '2009-01-01' AND '2009-01-20'
                AND EndDate BETWEEN '2009-01-01' AND '2009-01-20'
        )
SELECT  DISTINCT COALESCE(rs.ResourceID, rp.ResourceID)
FROM    rows rs
FULL JOIN
        rows rp
ON      rs.ResourceID = rp.ResourceID
        AND rp.rn = rs.rn - 1
WHERE   DATEDIFF(day, COALESCE(rp.EndDate, '2009-01-01'), COALESCE(rs.StartDate, '2009-01-20')) >= 5