T-SQL 识别中断的日期序列中的间隙

Question

请你帮忙解决我遇到的一个问题，我认为与 T-SQL 中的间隙和孤岛问题有关。我正在使用 SQL Server 2014。

我正在尝试使用日期列来识别 table/index 组合的连续出现次数，以区分断链。

请参阅下面的 T-SQL 来演示我正在努力实现的目标，特别是我如何计算出于演示目的而手动硬编码的 Rnk 列？

CREATE TABLE #test (RowID INT IDENTITY(1,1), FileDate DATE, TableName VARCHAR(100), IndexName VARCHAR(100), Rnk INT)

INSERT INTO #test (FileDate, TableName, IndexName, Rnk) 
VALUES
('2015-10-31', 't1', 'idx1', 1),
('2015-10-30', 't1', 'idx1', 2),

('2015-10-27', 't1', 'idx1', 1),
('2015-10-26', 't1', 'idx1', 2),
('2015-10-25', 't1', 'idx1', 3),

('2015-10-23', 't1', 'idx1', 1),
('2015-10-22', 't1', 'idx1', 2),
('2015-10-21', 't1', 'idx1', 3),
('2015-10-20', 't1', 'idx1', 4),
('2015-10-19', 't1', 'idx1', 5),
('2015-10-15', 't1', 'idx1', 1),
('2015-10-13', 't1', 'idx1', 1),
('2015-10-10', 't1', 'idx1', 1),
('2015-10-09', 't1', 'idx1', 2),

('2015-10-27', 't3', 'idx13', 1),
('2015-10-26', 't3', 'idx13', 2),
('2015-10-25', 't3', 'idx15', 1),
('2015-10-24', 't3', 'idx15', 2),
('2015-10-21', 't3', 'idx13', 1)

SELECT * FROM #test 

DROP TABLE #test

在我附加的屏幕截图中，突出显示的部分结果将显示我希望 Rnk 列对 t1/idx 在 2015-10-27 - 2015-10-25 之间的连续出现进行排序，但是将 2015-10-23 到 2015-10-19 的下一次出场次数重置。

有人可以帮我吗？

谢谢。

Answer 1

我会使用累积法：

select t.FileDate, t.TableName, t.IndexName,
       row_number() over (partition by tablename, indexname, grp order by rowid)
from (select t.*, sum(case when gap > 1 then 1 else 0 end) over (partition by tablename, indexname order by rowid) as grp
      from (select t.*, 
                   isnull(datediff(day, filedate, lag(filedate) over (partition by tablename, indexname order by rowid)), 1) as gap
            from #test t
           ) t
     ) t;

Answer 2

从日期中减去一系列数字 -- 您确定的组将具有常数值。然后你可以使用 row_number():

select t.*,
       row_number() over (partition by tablename, indexname,
                                       dateadd(day, - seqnum, filedate)
                          order by filedate desc
                         ) as rnk
from (select t.*,
             row_number() over (partition by tablename, indexname order by filedate) as seqnum
      from t
     ) t

Answer 3

类似于 Yogesh 的回答，他先于我。
（提示：不要指望在 phone 上输入答案会更快）

SELECT 
RowID, FileDate, TableName, IndexName, 
ROW_NUMBER() OVER (PARTITION BY TableName, IndexName,  DateRank ORDER BY FileDate DESC) AS Rnk
FROM
(
  SELECT *,
  SUM(DateGap) OVER (PARTITION BY TableName, IndexName ORDER BY FileDate DESC) AS DateRank
  FROM
  (
      SELECT RowID, FileDate, TableName, IndexName,
      --  Rnk as ExpRnk,
      CASE WHEN DATEDIFF(DAY, FileDate, LAG(FileDate) OVER (PARTITION BY TableName, IndexName ORDER BY FileDate DESC)) <= 1 THEN 0 ELSE 1 END AS DateGap
      FROM #Test
  ) q1
) q2
ORDER BY RowID;

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