具有案例/等級功能的LAG功能

Question

我在單個表中的列lbb_diag_value中有兩條消息（'usb_port_reset'，'onewire_cable'）。

我使用的兩列是：created_at（帶有時間戳），lbb_diag_value

問題：我想將one_wire_cable與所有連續的usb_port_reset消息相關聯，直到在表中找到另一個one_wire_cable。

例如：

         Created_at    lbb_diag_value
         1 PM          onewire_cable
         1:15 PM       usb_port_reset
         3:00 Pm       usb_port_reset
         12Pm          onewire_cable
         Some Time     usb_port_reset

Cuurent解決方案：我正在使用滯后函數和左連接，如果我沒有連續的usb_port_reset消息，這可以正常工作。

以下是我的代碼：

  WITH CTE
AS (
    SELECT e2.identifier
        ,e2.created_at
        ,e2.model
        ,e2.sw_pkg_version
        ,e2.type
        ,e2.lbb_diag_value
        ,e2.lbb_diag_type
    FROM (
        SELECT e1.identifier
            ,e1.created_at
            ,e1.model
            ,e1.sw_pkg_version
            ,e1.lbb_diag_type
            ,e1.lbb_diag_value
            ,e1.type
        FROM eld_messages e1
        WHERE e1.type = 'lbb_diag'
            AND e1.lbb_diag_type = 'usb_port_reset'
            AND { % condition created_filter % } e1.created_at { % endcondition % }
        ) e2
    )
    ,onewire
AS (
    SELECT e2.identifier
        ,e2.lbb_diag_value
        ,e2.created_at
        ,e2.type
        ,e2.lbb_diag_type
        ,e2.prev_lbb_diag_type
        ,e2.prev_created_at
        ,e2.prev_lbb_diag_value
        ,e2.model
        ,e2.sw_pkg_version
        ,e2.seqnum
    FROM (
        SELECT e1.identifier
            ,e1.created_at
            ,e1.lbb_diag_value
            ,e1.type
            ,e1.lbb_diag_type
            ,e1.event_id
            ,e1.model
            ,e1.sw_pkg_version
            ,LAG(e1.lbb_diag_type) OVER (
                PARTITION BY e1.identifier ORDER BY e1.created_at
                    ,e1.event_id DESC
                ) AS prev_lbb_diag_type
            ,LAG(e1.created_at) OVER (
                PARTITION BY e1.identifier ORDER BY e1.created_at
                    ,e1.event_id DESC
                ) AS prev_created_at
            ,LAG(e1.lbb_diag_value) OVER (
                PARTITION BY e1.identifier ORDER BY e1.created_at
                    ,e1.event_id
                ) AS prev_lbb_diag_value
            ,row_number() OVER (
                PARTITION BY e1.lbb_diag_type ORDER BY e1.created_at
                    ,e1.event_id DESC
                ) seqnum
        FROM eld_messages e1
        WHERE e1.type = 'lbb_diag'
            AND e1.lbb_diag_type IN (
                'onewire_cable'
                ,'usb_port_reset'
                )
            AND { % condition created_filter % } e1.created_at { % endcondition % }
        ORDER BY e1.identifier
            ,e1.created_at
        ) e2
    WHERE (
            e2.lbb_diag_type = 'usb_port_reset'
            AND e2.prev_lbb_diag_type = 'onewire_cable'
            )
        OR (
            CASE 
                WHEN e2.lbb_diag_type = 'usb_port_reset'
                    AND e2.prev_lbb_diag_type = 'usb_port_reset'
                    THEN e2.seqnum = 1
                END
            )
    )
SELECT cte.identifier
    ,cte.created_at
    ,cte.model
    ,cte.sw_pkg_version
    ,cte.type
    ,cte.lbb_diag_type
    ,cte.lbb_diag_value
    ,onewire.prev_lbb_diag_value AS onewire_lbb_diag_value
    ,onewire.prev_created_at AS onewire_created_at
FROM cte
LEFT JOIN onewire ON cte.identifier = onewire.identifier
    AND cte.created_at = onewire.created_at; 

Answer 1

是否可以使用延遲嵌套子選擇並過濾掉lbb_diag_value沒有變化的記錄？ 我沒有嘗試理解那個巨大查詢的整個上下文，如果你需要其他記錄，但是滯后可以是檢測邊界的好方法，看起來就像你需要的那樣。

FROM (
    SELECT * FROM (
        SELECT e1.identifier ,e1.created_at ,e1.lbb_diag_value ,e1.type ,e1.lbb_diag_type ,e1.event_id
            ,e1.model ,e1.sw_pkg_version
            ,LAG(e1.lbb_diag_type) OVER (PARTITION BY e1.identifier ORDER BY e1.created_at ,e1.event_id DESC) AS prev_lbb_diag_type
            ,LAG(e1.created_at) OVER ( PARTITION BY e1.identifier ORDER BY e1.created_at ,e1.event_id DESC) AS prev_created_at
            ,LAG(e1.lbb_diag_value) OVER ( PARTITION BY e1.identifier ORDER BY e1.created_at ,e1.event_id) AS prev_lbb_diag_value
            ,row_number() OVER (PARTITION BY e1.lbb_diag_type ORDER BY e1.created_at ,e1.event_id DESC) seqnum
        FROM eld_messages e1
        WHERE e1.type = 'lbb_diag' AND e1.lbb_diag_type IN ('onewire_cable' ,'usb_port_reset')
            AND { % condition created_filter % } e1.created_at { % endcondition % }
        ORDER BY e1.identifier, e1.created_at
    ) t
    WHERE lbb_diag_value != prev_lbb_diag_value
) e2

如果您需要所有記錄，您可以將其轉換為帶有連接的兩個子選擇（您已離開的選擇連接到檢測轉換的選擇），其中轉換（lbb_diag_value！= prev_lbb_diag_value）最終作為指示記錄的新列從一個值轉換到另一個值。

然后識別'onewire_cable'將是這樣的：

select * from (
...join...
) j where j.flip = 1 and j.lbb_diag_value = 'onewire_cable'