在Teradata的

Question

一個獨特的價值中創建組SESSION_ID --- ---狀態所需---

1C1A1111111 ---開始--- TRIP1 ---

1C1A1111111 ---？ - -Trip1 ---

1C1A1111111 ---？--- TRIP1 ---

1C1A1111111 ---？--- TRIP1 ---

1C1A1111111 ---？--- TRIP1 ---

1C1A1111111 ---停止--- TRIP1 ---

1C1A1111111 ---？------

1C1A1111111 ---？------

1C1A1111111 ---？------

1C1A1111111 ---？------

1C1A1111111 ---開始--- TRIP2 ---

1C1A1111111 ---？ --- Trip2- - ？？？

1C1A1111111 --- --- --- TRIP2

1C1A1111111 --- --- --- TRIP2

1C1A1111111 --- --- --- TRIP2

1C1A1111111 ---？--- TRIP2 ---

1C1A1111111 ---？--- TRIP2 ---

1C1A1111111 ---？--- TRIP2 ---

1C1A1111111 ---停止--- TRIP2 ---

Answer 1

CASE -- check if current row is between start and stop 
    WHEN Last_Value(status IGNORE NULLS) 
     Over (PARTITION BY session_id 
       ORDER BY ts 
       ROWS Unbounded Preceding) = 'start' 
    OR status = 'stop' 

     -- increase trip number whenever status = 'start' 
    THEN Sum(CASE WHEN status = 'start' THEN 1 END) 
     Over (PARTITION BY session_id 
       ORDER BY ts 
       ROWS Unbounded Preceding) 
END