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SQL Server, encuentre una secuencia arbitraria de valores

Esto seleccionará a todos los clientes con al menos dos acciones consecutivas del mismo tipo.

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
        )

Esta es la consulta más eficiente solo para la acción 2 :

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
        )

Actualización 2:

Para seleccionar rangos ininterrumpidos:

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

Esta consulta calcula dos series:una devuelve ORDER BY lastlogin contiguos , el segundo particiona por action adicionalmente:

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

Mientras la diferencia entre los dos esquemas sea la misma, las series son ininterrumpidas. Cada interrupción rompe la serie.

Esto significa que la combinación de (action, diff ) define los grupos ininterrumpidos.

Podemos agrupar por action, diff , busca MAX y MIN dentro de los grupos y filtrarlos.

Si necesita seleccionar 14 filas en lugar de 14 días consecutivos, solo filtre en COUNT(*) en lugar de DATEDIFF .