LAG函数和NULLS

Question

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

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我正在使用滞后函数来获取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

为ITEM 2填写lag_Value_1,2,3,4,5 ....的任何帮助吗？

Answer 1

您是否想要三个参数形式的滞后？

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

这三个参数是：

• 滞后值。
• 要返回的行数。
• 默认值。

Answer 2

我觉得以下是您要寻找的内容：

  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