Question

我正在使用mysql数据库存储大量卫星数据，这些数据集有很多数据空白。我希望在该点附近用1小时（或更短）的平均值替换NULL值。到目前为止，我已经找到了如何用之前的已知值替换NULL值：

UPDATE mytable
SET number = (@n := COALESCE(number, @n))
ORDER BY date;

来自这篇文章：SQL QUERY replace NULL value in a row with a value from the previous known value

我的表格似乎是

+---------------------+--------+
| date                | P_f    |
+---------------------+--------+
| 2001-01-01 20:20:00 |   1.88 | 
| 2001-01-01 20:25:00 |   NULL | 
| 2001-01-01 20:30:00 |   NULL | 
| 2001-01-01 20:35:00 |   1.71 | 
| 2001-01-01 20:40:00 |   NULL | 
| 2001-01-01 20:45:00 |   NULL | 
| 2001-01-01 20:50:00 |   NULL | 
| 2001-01-01 20:55:00 |  1.835 | 
| 2001-01-01 21:00:00 |  1.918 | 
| 2001-01-01 21:05:00 |  1.968 | 
| 2001-01-01 21:10:00 |  2.004 | 
| 2001-01-01 21:15:00 |  1.924 | 
| 2001-01-01 21:20:00 | 1.8625 | 
| 2001-01-01 21:25:00 |   1.94 | 
| 2001-01-01 21:30:00 | 2.0375 | 
| 2001-01-01 21:35:00 |  1.912 |

我想将NULL值替换为该日期时间周围的平均值。例如，我想替换，

| 2001-01-01 20:50:00 |   NULL |

平均值

select AVG(P_f) from table where date between '2001-01-01 20:30' and '2001-01-01 21:10';

保

Answer 1

不是我承认的最优雅，但它应该能得到你想要的东西。

我不确定您希望如何处理小时平均值为NULL的NULL值。在下面的示例中，这些将更新为-1。

create table myTable
(myDate datetime not null,
P_f decimal(10,5) default null
);

insert into myTable(myDate,P_f) values ('2001-01-01 20:20:00',1.88);
insert into myTable(myDate,P_f) values ('2001-01-01 20:25:00',NULL);
insert into myTable(myDate,P_f) values ('2001-01-01 20:30:00',NULL);
insert into myTable(myDate,P_f) values ('2001-01-01 20:35:00',1.71);
insert into myTable(myDate,P_f) values ('2001-01-01 20:40:00',NULL);
insert into myTable(myDate,P_f) values ('2001-01-01 20:45:00',NULL);
insert into myTable(myDate,P_f) values ('2001-01-01 20:50:00',NULL);
insert into myTable(myDate,P_f) values ('2001-01-01 20:55:00',1.835);
insert into myTable(myDate,P_f) values ('2001-01-01 21:00:00',1.918);
insert into myTable(myDate,P_f) values ('2001-01-01 21:05:00',1.968);
insert into myTable(myDate,P_f) values ('2001-01-01 21:10:00',2.004);
insert into myTable(myDate,P_f) values ('2001-01-01 21:15:00',1.924);
insert into myTable(myDate,P_f) values ('2001-01-01 21:20:00',1.8625);
insert into myTable(myDate,P_f) values ('2001-01-01 21:25:00',1.94);
insert into myTable(myDate,P_f) values ('2001-01-01 21:30:00',2.0375);
insert into myTable(myDate,P_f) values ('2001-01-01 21:35:00',1.912);
insert into myTable(myDate,P_f) values ('2001-01-02 20:40:00',NULL);

-- Insert copy of null value P_f rows into myTable with 1 hour average about myDate 
insert into myTable
(myDate,P_f)
select t.myDate,ifnull((select avg(P_f) from myTable t1 where t1.myDate between t.myDate - interval 1 hour and t.myDate +interval 1 hour),-1) as hourAvg
from myTable t
where t.P_f is null;

-- delete rows where P_f is null
delete from myTable
where P_f is null;

MYSQL QUERY用平均值替换行中的NULL值

1 个答案: