我在 Ingres 表中有类似这样的数据；
REF FROM_DATE TO_DATE
A 01.04.1997 01.04.1998
A 01.04.1998 27.05.1998
A 27.05.1998 01.04.1999
B 01.04.1997 01.04.1998
B 01.04.1998 26.07.1998
B 01.04.2012 01.04.2013
一些 refs 有从 min(from_date) 到 max(to_date) 的连续周期，但有些在周期中有间隙。
我想知道在 Ingres SQL 中识别哪些参考在日期期间有间隙的方法。
我将其作为调用 Ingres sql 命令的 Unix shell 脚本来执行。
请指教。
我不熟悉 Ingres 中的日期函数。让我假设这-会在几天内获得两个日期之间的差异。
如果数据中没有重叠，那么你可以很容易地做你想做的事。如果没有间隙，则最小日期和最大日期之间的差异与每行差异的总和相同。如果差值大于 0，则存在间隙。
所以：
select ref,
((max(to_date) - min(from_date)) -
sum(to_date - from_date)
) as total_gaps
from t
group by ref;
我相信这将适用于您的情况。在其他情况下，可能会出现“偏离 1”的问题，具体取决于结束日期是否包含在期间中。
此查询在 SQL SERVER 中有效。PARTITION是一个ANSI SQL命令，不知道INGRES是否支持。如果支持分区可能你会有一个等价于Dense_Rank()
select *
INTO #TEMP
from (
select 'A' as Ref, Cast('1997-01-04' as DateTime) as From_date, Cast('1998-01-04' as DateTime) as to_date
union
select 'A' as Ref, Cast('1998-01-04' as DateTime) as From_date, Cast('1998-05-27' as DateTime) as to_date
union
select 'A' as Ref, Cast('1998-05-27' as DateTime) as From_date, Cast('1999-01-04' as DateTime) as to_date
union
select 'B' as Ref, Cast('1997-01-04' as DateTime) as From_date, Cast('1998-01-04' as DateTime) as to_date
union
select 'B' as Ref, Cast('1998-01-04' as DateTime) as From_date, Cast('1998-07-26' as DateTime) as to_date
union
select 'B' as Ref, Cast('2012-01-04' as DateTime) as From_date, Cast('2013-01-04' as DateTime) as to_date
) X
SELECT *
FROM
(
SELECT Ref, Min(NewStartDate) From_Date, MAX(To_Date) To_Date, COUNT(1) OVER (PARTITION BY Ref ) As [CountRanges]
FROM
(
SELECT Ref, From_Date, To_Date,
NewStartDate = Range_UNTIL_NULL.From_Date + NUMBERS.number,
NewStartDateGroup = DATEADD(d,
1 - DENSE_RANK() OVER (PARTITION BY Ref ORDER BY Range_UNTIL_NULL.From_Date + NUMBERS.number),
Range_UNTIL_NULL.From_Date + NUMBERS.number)
FROM
(
--This subquery is necesary needed to "expand the To_date" to the next day and allowing it to be null
SELECT
REF, From_date, DATEADD(d, 1, ISNULL(To_Date, From_Date)) AS to_date
FROM #Temp T1
WHERE
NOT EXISTS ( SELECT *
FROM #Temp t2
WHERE T1.Ref = T2.Ref and T1.From_Date > T2.From_Date AND T2.To_Date IS NULL
)
) AS Range_UNTIL_NULL
CROSS APPLY Enumerate ( ABS(DATEDIFF(d, From_Date, To_Date))) AS NUMBERS
) X
GROUP BY Ref, NewStartDateGroup
) OVERLAPED_RANGES_WITH_COUNT
-- WHERE OVERLAPED_RANGES_WITH_COUNT.CountRanges >= 2 --This filter is for identifying ranges that have at least one gap
ORDER BY Ref, From_Date
给定示例的结果是：
Ref From_Date To_Date CountRanges
---- ----------------------- ----------------------- -----------
A 1997-01-04 00:00:00.000 1999-01-05 00:00:00.000 1
B 1997-01-04 00:00:00.000 1998-07-27 00:00:00.000 2
B 2012-01-04 00:00:00.000 2013-01-05 00:00:00.000 2
如您所见，那些具有 "CountRanges" > 1 的参考至少有一个差距
这个答案远远超出了最初的问题，因为：