SQL，仅对第一个空值进行向后填充，仅对最后一个空值进行前向填充，对其他空值进行线性插值

Question

如何在 bigquery 中对具有列时间戳的表中的列进行向后、向前和线性插值填充？

我有这张桌子：

时间戳	霉菌
1	空
2	空
3	69
4	空
5	71
6	72
7	空

我期望这样的结果：

时间戳	霉菌
1	69
2	69
3	69
4	70
5	71
6	72
7	72

Answer 1

请参阅下面的查询，

WITH input_data as (
  SELECT 1 as _timestamp,   null as my_col
  UNION ALL
  SELECT 2 as _timestamp,   null as my_col
  UNION ALL
  SELECT 3 as _timestamp,   69 as my_col
  UNION ALL
  SELECT 4 as _timestamp,   null as my_col
  UNION ALL
  SELECT 5 as _timestamp,   71 as my_col
  UNION ALL
  SELECT 6 as _timestamp,   72 as my_col
  UNION ALL
  SELECT 7 as _timestamp,   null as my_col
) SELECT *,IFNULL(IFNULL(my_col,FIRST_VALUE(my_col IGNORE NULLS)
                  OVER (item_window ROWS BETWEEN CURRENT ROW AND UNBOUNDED FOLLOWING )
                  ), -- inner ifnull/firstvalue block to select first not null value
           LAG(my_col) OVER (ORDER BY _timestamp, my_col)) AS new_value --outer ifnull/lag block to correct trailing nulls/blanks
FROM input_data
WINDOW item_window as (ORDER BY input_data._timestamp)

在屏幕截图中查看查询输出