计算数据集的持续时间

Question

我在 SQL 中有一组数据，如下所示：

╔═══════════╦═══════╗
║ TimeStamp ║ State ║
╠═══════════╬═══════╣
║  7:10 AM  ║   A   ║
║  7:11 AM  ║   A   ║
║  7:12 AM  ║   A   ║
║  7:13 AM  ║   B   ║
║  7:14 AM  ║   B   ║
║  7:15 AM  ║   A   ║
║  7:16 AM  ║   A   ║
║  7:17 AM  ║   C   ║
║  7:18 AM  ║   C   ║
╚═══════════╩═══════╝

我正在尝试计算每个状态的持续时间。但是，我想分离每个状态序列并分别计算它们的差异，同时分离重复的状态。所以我希望上面的数据 return 如下所示：

╔═══════╦════════════════════╗
║ State ║ Duration (minutes) ║
╠═══════╬════════════════════╣
║   A   ║         2          ║
║   B   ║         1          ║
║   A   ║         1          ║
║   C   ║         1          ║
╚═══════╩════════════════════╝

有人可以帮忙吗？我如何编写一个 SQL 查询 return 给我这个数据？

谢谢！

Answer 1

好吧，我假设需要的是 MS SQL 服务器。

为了达到预期的结果（其中 C 的持续时间为 1）：

select    
    state, MIN(TimeStamp) StartsAt, EndsAt, datediff(minute,MIN(TimeStamp),EndsAt) DurationMinutes
from (
        select
                t1.state, t1.TimeStamp
                , ISNULL(ca.EndsAt, (select max(timestamp) from table1) ) EndsAt
        from table1 t1
        outer apply (
                  select top (1) t2.timestamp as EndsAt
                  from table1 t2
                  where t1.state <> t2.state and t1.TimeStamp < t2.TimeStamp
                  order by t2.TimeStamp
              ) ca
    ) as derived
group by     
    state, EndsAt

对于数据样本，有人可能会争辩说 C 的持续时间是未知的，因为状态尚未改变。在那种情况下它有点简单：

select    
    state, MIN(TimeStamp) StartsAt, EndsAt, datediff(minute,MIN(TimeStamp),EndsAt) DurationMinutes
from (
        select
                t1.state, t1.TimeStamp ,ca.EndsAt
        from table1 t1
        outer apply (
                  select top (1) t2.timestamp as EndsAt
                  from table1 t2
                  where t1.state <> t2.state and t1.TimeStamp < t2.TimeStamp
                  order by t2.TimeStamp
              ) ca
    ) as derived
group by     
    state, EndsAt

http://sqlfiddle.com/#!6/f0dd7e/9

Answer 2

您没有提到 RDBMS，所以这里是适用于任何数据库的答案。如果您需要快速解决方案，请提及您使用的 SQL 基数，以便您能够使用此类查询所需的某些特定 functions/commands（访问上一条、下一条记录...）。

SELECT MIN(timeStamp),MAX(timeStamp),State
FROM(
     SELECT TimeStamp,State,(SELECT count(*) FROM t 
                         where state<>t1.state 
                         and TimeStamp<t1.TimeStamp) as Grp 
                         from t as t1
     ) as t2
GROUP BY State,Grp

SQLFiddle demo

计算数据集的持续时间

Calculate duration of sets of data

sql

gaps-and-islands