sql查询和计数

我有一张桌子

id  date      state
1   10.01.01  reg
2   08.01.01  reg
3   05.01.01  check
4   02.01.01  check
5   01.01.01  reg

想展示这样的结果吗

count   reg
5       1

e、 g仅当先前状态为“检查”时，才应计算“reg”状态的总和。

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请帮助我或给出正确的解决方法，在SQL Server 2012及以上版本中，您可以使用LAG访问前一行值：

SQL SERVER 2012

;WITH MyCTE AS
(
  select id, date,state,lag(state,1) over(order by id) as prevstate
  from Table1
)
SELECT COUNT(*),SUM(CASE WHEN state = 'reg' AND prevstate = 'check' THEN 1 ELSE 0 END)
FROM MyCTE

ORACLE

With T AS
(
select "id", "date", "state",  lag("state",1) over(order by "id") as "prevstate"
from Table1
)
SELECT COUNT(*),SUM(CASE WHEN "state" = 'reg' AND "prevstate" = 'check' THEN 1 ELSE 0 END)  
FROM T

MySQL

SELECT COUNT(*),SUM(CASE WHEN state = 'reg' AND prevstate = 'check' THEN 1 ELSE 0 END)
FROM
(
  SELECT T1.ID,T1.Date,T1.state,T2.state AS prevstate
  FROM Table1 T1
  LEFT JOIN Table1 T2
  ON T1.ID - 1 = T2.ID
) AS T

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事实上，第三种情况几乎适用于所有情况。

您的DB引擎和版本是什么