SQLite填充空值

Question

所以我有一些带有NULL值的表，我希望用最后一个有效值填充。我可以选择一个带有更正列的新表，但我不确定如何更新数据库上的值，有人可以帮我更新语句吗？

select b.timeStamp, 
       b.var_5, 
     (select a.var_5  from wme_test as a where a.timeStamp<=b.timeStamp  and a.var_5 <> 'NULL' order by timestamp desc limit 1 )  as correctedVar5 
from wme_test as b

此查询的输出是

Answer 1

您可以使用相关更新来执行此操作。

update wme_test 
set var5 = (select var5 
            from wme_test 
            where tm >= wme_test.tm and var5 is not null 
            order by tm limit 1)
where var5 is null

Sample Fiddle

请注意，表中最早的时间戳无法使用此更新。如果之前为null，它仍为null。