LAG 函数和 NULLS

Question

所以我正在尝试使用 LAG 函数 (Google BigQuery)，我的第一个值是 NULL。

我正在使用滞后函数来获得 lag_Value_1,lag_Value_2... 在这里：

SELECT ITEM,row_A,row_B,date,Value_1,Value_2,Value_3,Value_4,Value_5,
         LAG(Value_1,0) OVER (PARTITION BY ITEM ORDER BY row_A asc) as lag_Value_1,
         LAG(Value_2,0) OVER (PARTITION BY ITEM ORDER BY row_A asc) as lag_Value_2,
         LAG(Value_3,0) OVER (PARTITION BY ITEM ORDER BY row_A asc) as lag_Value_3,
         LAG(Value_4,0) OVER (PARTITION BY ITEM ORDER BY row_A asc) as lag_Value_4,
         LAG(Value_5,0) OVER (PARTITION BY ITEM ORDER BY row_A asc) as lag_Value_5
FROM table

对填写第 2 项的 lag_Value_1,2,3,4,5.... 有帮助吗？

Answer 1

你想要滞后的三参数形式吗？

SELECT ITEM, row_A, row_B, date, Value_1, Value_2, Value_3, Value_4, Value_5,
       LAG(Value_1, 1, 0) OVER (PARTITION BY ITEM ORDER BY row_A asc) as lag_Value_1,
       LAG(Value_2, 1, 0) OVER (PARTITION BY ITEM ORDER BY row_A asc) as lag_Value_2,
       LAG(Value_3, 1, 0) OVER (PARTITION BY ITEM ORDER BY row_A asc) as lag_Value_3,
       LAG(Value_4, 1, 0) OVER (PARTITION BY ITEM ORDER BY row_A asc) as lag_Value_4,
       LAG(Value_5, 1, 0) OVER (PARTITION BY ITEM ORDER BY row_A asc) as lag_Value_5
FROM table

三个参数是：

滞后值。
要返回的行数。
默认值。

Answer 2

我觉得下面是你要找的：

  LAST_VALUE(Value_1 IGNORE NULLS) OVER (PARTITION BY ITEM ORDER BY row_A ASC) AS lag_Value_1,
  LAST_VALUE(Value_2 IGNORE NULLS) OVER (PARTITION BY ITEM ORDER BY row_A ASC) AS lag_Value_2,
  LAST_VALUE(Value_3 IGNORE NULLS) OVER (PARTITION BY ITEM ORDER BY row_A ASC) AS lag_Value_3,
  LAST_VALUE(Value_4 IGNORE NULLS) OVER (PARTITION BY ITEM ORDER BY row_A ASC) AS lag_Value_4,
  LAST_VALUE(Value_5 IGNORE NULLS) OVER (PARTITION BY ITEM ORDER BY row_A ASC) AS lag_Value_5

LAG 函数和 NULLS

LAG function and NULLS

sql

null

google-bigquery

lag