采用该试样数据:
CREATE TABLE MyTable (ID INT, Date DATETIME, Allocation INT);
INSERT INTO MyTable VALUES (1, {d '2012-01-01'}, 0);
INSERT INTO MyTable VALUES (2, {d '2012-01-02'}, 2);
INSERT INTO MyTable VALUES (3, {d '2012-01-03'}, 0);
INSERT INTO MyTable VALUES (4, {d '2012-01-04'}, 0);
INSERT INTO MyTable VALUES (5, {d '2012-01-05'}, 0);
INSERT INTO MyTable VALUES (6, {d '2012-01-06'}, 5);
GO
尝试这种情况:
WITH DateGroups (ID, Date, Allocation, SeedID) AS (
SELECT MyTable.ID, MyTable.Date, MyTable.Allocation, MyTable.ID
FROM MyTable
LEFT JOIN MyTable Prev ON Prev.Date = DATEADD(d, -1, MyTable.Date)
AND Prev.Allocation = 0
WHERE Prev.ID IS NULL
AND MyTable.Allocation = 0
UNION ALL
SELECT MyTable.ID, MyTable.Date, MyTable.Allocation, DateGroups.SeedID
FROM MyTable
JOIN DateGroups ON MyTable.Date = DATEADD(d, 1, DateGroups.Date)
WHERE MyTable.Allocation = 0
), StartDates (ID, StartDate, DayCount) AS (
SELECT SeedID, MIN(Date), COUNT(ID)
FROM DateGroups
GROUP BY SeedID
), EndDates (ID, EndDate) AS (
SELECT SeedID, MAX(Date)
FROM DateGroups
GROUP BY SeedID
)
SELECT StartDates.StartDate, EndDates.EndDate, StartDates.DayCount
FROM StartDates
JOIN EndDates ON StartDates.ID = EndDates.ID;
查询的第一部分是一个递归SELECT,这是由是所有行锚定分配= 0,并且其前一天或者不存在或者分配!= 0.这实际上会返回ID:1和3,这是您想要返回的时间段的开始日期。
该查询的递归部分从锚点行开始,并查找也具有分配= 0的所有后续日期。SeedID通过所有迭代跟踪锚定的ID。
到目前为止的结果是这样的:
ID Date Allocation SeedID
----------- ----------------------- ----------- -----------
1 2012-01-01 00:00:00.000 0 1
3 2012-01-03 00:00:00.000 0 3
4 2012-01-04 00:00:00.000 0 3
5 2012-01-05 00:00:00.000 0 3
下一个子查询使用简单GROUP BY过滤掉所有的开始日期为每个SeedID,并且还计算了天。
最后一个子查询与结束日期完成相同的事情,但是这次不需要日计数,因为我们已经有了这个。
最终的SELECT查询将这两者结合在一起组合起始日期和结束日期,并将它们与日计数一起返回。
@ istari是结束日期您的表结构中的一列 – Devjosh 2012-02-14 10:09:04
您尝试过使用光标吗?或者您不需要游标 – Vikram 2012-02-14 10:31:31
您是指“间隔一天”中的“连续”,还是指“当行按日期排序时邻近”?即每个唯一的日期是否在'日期'列中恰好出现一次? – gcbenison 2012-02-14 13:40:25