SQL Server，查找任意值序列

Question

假设我们有一个维护表

Customer LastLogin ActionType
1        12/1/2007 2
1        12/2/2007 2
etc.

我们想要一份所有客户的列表，这些客户在给定年份的任何时候都有一个或多个连续 14 天的连续登录操作类型 2。

我当然可以很容易地用代码做到这一点，甚至在小集合上也相当快。在 SQL 中有没有非游标的方法？

Answer 1

这将选择至少连续执行两次相同类型操作的所有客户。

WITH    rows AS 
        (
        SELECT  customer, action,
                ROW_NUMBER() OVER (PARTITION BY customer ORDER BY lastlogin) AS rn
        FROM    mytable
        )
SELECT  DISTINCT customer
FROM    rows rp
WHERE   EXISTS
        (
        SELECT  NULL
        FROM    rows rl
        WHERE   rl.customer = rp.customer
                AND rl.rn = rp.rn + 1
                AND rl.action = rp.action
        )

下面是针对操作 2 的更高效的查询:

WITH    rows AS 
        (
        SELECT  customer, ROW_NUMBER() OVER (PARTITION BY customer ORDER BY lastlogin) AS rn
        FROM    mytable
        WHERE   action = 2
        )
SELECT  DISTINCT customer
FROM    rows rp
WHERE   EXISTS
        (
        SELECT  NULL
        FROM    rows rl
        WHERE   rl.customer = rp.customer
                AND rl.rn = rp.rn + 1
        )

更新 2:

要选择不间断的范围:

WITH    rows AS 
        (
        SELECT  customer, action, lastlogin
                ROW_NUMBER() OVER (PARTITION BY customer ORDER BY lastlogin) AS rn
                ROW_NUMBER() OVER (PARTITION BY customer, action ORDER BY lastlogin) AS series
        FROM    mytable
        )
SELECT  DISTINCT customer
FROM    (
        SELECT  customer
        FROM    rows rp
        WHERE   action
        GROUP BY
                customer, actioncode, series - rn
        HAVING
                DETEDIFF(day, MIN(lastlogin), MAX(lastlogin)) >= 14
        ) q

此查询计算两个系列:一个返回连续的 ORDER BY laSTLogin，第二个按 action 划分:

action  logindate rn  series diff = rn - series
1       Jan 01    1   1      0
1       Jan 02    2   2      0
2       Jan 03    3   1      2
2       Jan 04    4   2      2
1       Jan 05    5   3      2
1       Jan 06    6   4      2

只要两种方案的区别相同，系列不间断。每次中断都会打断系列。

这意味着 (action, diff) 的组合定义了不间断的组。

我们可以按action、diff 进行分组，在组中找到MAX 和MIN 并对其进行过滤。

如果您需要选择 14 行而不是连续 14 天，只需过滤 COUNT(*) 而不是 DATEDIFF.