Sql server 仅基于一个字段,选择与以前记录相比发生更改的记录
考虑以下示例数据Sql server 仅基于一个字段,选择与以前记录相比发生更改的记录,sql-server,Sql Server,考虑以下示例数据 | SN | DateTime | Status | |----|-----------------------|--------| | 1 | '2015-01-01 00:30:00' | OPEN | | 2 | '2015-01-01 00:35:00' | OPEN | | 3 | '2015-01-01 00:40:00' | CLOSED | | 4 | '2015-01-01 00:50:00' | OPEN | |
| SN | DateTime | Status |
|----|-----------------------|--------|
| 1 | '2015-01-01 00:30:00' | OPEN |
| 2 | '2015-01-01 00:35:00' | OPEN |
| 3 | '2015-01-01 00:40:00' | CLOSED |
| 4 | '2015-01-01 00:50:00' | OPEN |
| 5 | '2015-01-01 01:10:00' | OPEN |
| 6 | '2015-01-01 01:15:00' | CLOSED |
| 7 | '2015-01-01 01:20:00' | CLOSED |
| 8 | '2015-01-01 01:30:00' | OPEN |
| 9 | '2015-01-01 01:40:00' | OPEN |
| 10 | '2015-01-01 01:52:00' | OPEN |
| 11 | '2015-01-01 01:55:00' | CLOSED |
| 12 | '2015-01-01 02:15:00' | OPEN |
| 13 | '2015-01-01 02:30:00' | OPEN |
我需要选择列“Status”的值与以前的记录不同的记录。应始终返回第一条记录
我可以使用SQL Server中的For循环来完成,但我想要一个更好的解决方案。是否可以在单个SELECT语句中执行此操作?查询应返回序列为1、3、4、6、8、11和12的行。您可以使用LAG获取以前的状态值,然后在外部查询的WHERE子句中使用此值以获取所需的:
SELECT SN, [DateTime], Status
FROM (
SELECT SN, [DateTime], Status,
LAG(Status) OVER (ORDER BY [DateTime]) AS prevStatus
FROM mytable ) t
WHERE COALESCE(prevStatus, '') <> Status
或者在没有延迟的情况下,您可以使用此查询
select * from (SELECT TOP 1 SN, [DateTime], Status from mytable order by SN) as s
UNION ALL
SELECT T.SN, t.[DateTime], t.Status
FROM mytable t
inner join mytable t2
on t.SN=t2.SN+1 AND t.status <> t2.status
我们可以使用Union运算符,然后在Id+1上自联接表
select * from Delta where id = 1
UNION
select D.*from
Delta D JOIN Delta DL On D.Id = Dl.Id +1
AND
D.Status <> DL.Status
什么版本的sql server?2012 Express@wewewesthemenacei我想知道sql server中是否有LAG2008@PareshJ从SQL Server 2012开始提供。