Question

如何从sql

中的以下一组或多个记录中找到最小值

Date                       Values
-------------------------  ------
 2013-07-20 18:05:38.599   257
 2013-07-20 18:06:39.264   118
 2013-07-20 18:07:39.51    142
 2013-07-20 18:08:39.67    138
 2013-07-20 18:09:40.279   123
 2013-07-20 18:10:40.697   115
 2013-07-20 18:11:41.158   124
 2013-07-20 18:12:41.327   128
 2013-07-20 18:13:41.797   533
 2013-07-20 18:14:42.345   129
 2013-07-20 18:15:42.694   124
 2013-07-20 18:16:43.222   114
 2013-07-20 18:17:43.715   119
 2013-07-20 18:18:44.162   126

我需要找到时间戳每3分钟的最小值。任何人都可以建议一个查询来工作吗??

Answer 1

始终指定您的dbms，并在您的问题中提供CREATE TABLE和INSERT语句。

create table test (
  date timestamp,
  value integer
);
insert into test values
('2013-07-20 18:05:38.599',   257),
('2013-07-20 18:06:39.264',   118),
('2013-07-20 18:07:39.51',    142),
('2013-07-20 18:08:39.67',    138),
('2013-07-20 18:09:40.279',   123),
('2013-07-20 18:10:40.697',   115),
('2013-07-20 18:11:41.158',   124),
('2013-07-20 18:12:41.327',   128),
('2013-07-20 18:13:41.797',   533),
('2013-07-20 18:14:42.345',   129),
('2013-07-20 18:15:42.694',   124),
('2013-07-20 18:16:43.222',   114),
('2013-07-20 18:17:43.715',   119),
('2013-07-20 18:18:44.162',   126);

使用平台的日期/时间功能生成“桶”虚拟表，每个表包含三分钟的间隔。完全你如何做到这一点因SQL平台而异，因为日期/时间函数在SQL平台之间变化很大。我正在使用PostgreSQL，因此我将在公共表表达式中使用其generate_series（）函数。

with buckets as (
  select n as start_time, n + interval '3' minute as end_time
  from generate_series(timestamp '2013-07-20 18:05:38.599', 
                       timestamp '2013-07-20 18:18:44.162', 
                       '3 minutes') n
)
select min(test.value), start_time, end_time
from test
inner join buckets on test.date >= start_time and test.date < end_time
group by start_time, end_time
order by start_time;

118  2013-07-20 18:05:38.599  2013-07-20 18:08:38.599
115  2013-07-20 18:08:38.599  2013-07-20 18:11:38.599
124  2013-07-20 18:11:38.599  2013-07-20 18:14:38.599
114  2013-07-20 18:14:38.599  2013-07-20 18:17:38.599
119  2013-07-20 18:17:38.599  2013-07-20 18:20:38.599

通过将sql中的时间戳分组来查找最小值

1 个答案: