Sql 计算数据集的持续时间

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   ║
╚═══════════╩═══════╝

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

我试图计算每个状态的持续时间。但是，我想分离每个状态序列，分别计算它们的差异，分离重复的状态。因此，我希望上述数据返回如下内容：

╔═══════════╦═══════╗
║ 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   ║
╚═══════════╩═══════╝

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

有人能帮忙吗？如何编写返回此数据的SQL查询

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谢谢大家!

我假设需要MS SQL Server

为达到C持续时间为1的预期结果：

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，有人可能会说C的持续时间是未知的，因为状态尚未改变。在这种情况下，它更简单一些：

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

---

您没有提到您的RDBMS，所以这里的答案适用于任何数据库。如果您需要快速解决方案，请说明您使用的SQL库，以便能够使用某些特定的函数/命令访问上一条记录、下一条记录，。。。需要这样一个查询

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

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请问什么牌子的SQL？e、 甲骨文？MSsql？它还可以对解决方案选项产生很大的影响：是否有日期列？除了状态列之外是否还有顺序？正如您所看到的，使用简单的GROUPBY在这里不起作用，因为您实际上需要State列的子组，因此我的问题是。