研究生连续几天，缺口和岛屿，禁忌

Question

SQL FIDDLE

我有以下数据库表：

日期		名称
2014-08-10	bob
2014-08-10	起诉
2014-08-11	bob
2014-08-11	麦克风
2014-08-12	bob
2014-08-12	麦克风
2014-08-05	bob
2014-08-06	bob

您使用了错误的逻辑。基本上，你想要的日期是连续的，所以你想从日期中减去序列：

SELECT t.Name, COUNT(*) as frequency
FROM (SELECT o.*,
row_number() OVER (PARTITION BY Name ORDER BY Date) as seqnum
FROM orders o
) t
GROUP BY Name, date - seqnum * interval '1 day';

这里有一个db<gt；不停摆弄

Postgresql中Date数据类型Demo1的缺口和孤岛问题：运行此：

drop table if exists foobar; 
CREATE TABLE foobar( tick text, date_val date ); 
insert into foobar values('XYZ', '2021-01-03');  --island 1 has width 2
insert into foobar values('XYZ', '2021-01-04');  --island 1
insert into foobar values('XYZ', '2021-05-09');  --island 2 has width 3
insert into foobar values('XYZ', '2021-05-10');  --island 2 
insert into foobar values('XYZ', '2021-05-11');  --island 2
insert into foobar values('XYZ', '2021-07-07');  --island 3 has width 4
insert into foobar values('XYZ', '2021-07-08');  --island 3
insert into foobar values('XYZ', '2021-07-09');  --island 3
insert into foobar values('XYZ', '2021-07-10');  --island 3 
insert into foobar values('XYZ', '2022-10-10');  --island 4 has width 1
select * from foobar; 
select tick, island_width, min_val, max_val, 
min_val - lag(max_val) over (order by max_val) 
as gap_width from  
( 
select tick, count(*) as island_width, 
min(date_val) min_val, max(date_val) max_val 
from ( 
select t.*, 
row_number() over ( partition by tick order by date_val ) as seqnum 
from foobar t where tick = 'XYZ' 
) t 
group by tick, date_val - seqnum * interval '1 day' 
) t2 order by max_val desc

按顺序打印日期的间隙和孤岛：

┌──────┬────────────┐ 
│ tick │  date_val  │ 
├──────┼────────────┤  
│ XYZ  │ 2021-01-03 │ 
│ XYZ  │ 2021-01-04 │ 
│ XYZ  │ 2021-05-09 │ 
│ XYZ  │ 2021-05-10 │ 
│ XYZ  │ 2021-05-11 │ 
│ XYZ  │ 2021-07-07 │  
│ XYZ  │ 2021-07-08 │  
│ XYZ  │ 2021-07-09 │  
│ XYZ  │ 2021-07-10 │  
│ XYZ  │ 2022-10-10 │  
└──────┴────────────┘ 
┌──────┬──────────────┬────────────┬────────────┬───────────┐ 
│ tick │ island_width │  min_val   │  max_val   │ gap_width │ 
├──────┼──────────────┼────────────┼────────────┼───────────┤ 
│ XYZ  │            1 │ 2022-10-10 │ 2022-10-10 │       457 │ 
│ XYZ  │            4 │ 2021-07-07 │ 2021-07-10 │        57 │ 
│ XYZ  │            3 │ 2021-05-09 │ 2021-05-11 │       125 │ 
│ XYZ  │            2 │ 2021-01-03 │ 2021-01-04 │         ¤ │ 
└──────┴──────────────┴────────────┴────────────┴───────────┘ 

列island_width给出了连续数据的宽度。gap_width为您提供缺失数据的宽度。

Postgresql中Integer数据类型Demo2的缺口和孤岛问题：

运行此：

drop table if exists foobar; 
CREATE TABLE foobar( tick text, the_value int); 
insert into foobar values('XYZ', -5);  --island 1 has width 2 
insert into foobar values('XYZ', -4);  --end island 1 
insert into foobar values('XYZ', 0);   --island 2 has width 3 
insert into foobar values('XYZ', 1);   --island 2 
insert into foobar values('XYZ', 2);   --end island 2 
insert into foobar values('XYZ', 34);  --island 3 has width 4 
insert into foobar values('XYZ', 35);  --island 3 
insert into foobar values('XYZ', 36);  --island 3 
insert into foobar values('XYZ', 37);  --island 3 
insert into foobar values('XYZ', 85);  --island 4 has width 1 

select * from foobar; 

select tick, island_width, min_val, max_val, 
min_val - lag(max_val) over (order by max_val) 
as gap_width from 
( 
select tick, count(*) as island_width, 
min(the_value) min_val, max(the_value) max_val 
from ( 
select t.*, 
row_number() over ( partition by tick order by the_value) as seqnum 
from foobar t where tick = 'XYZ' 
) t 
group by tick, the_value - seqnum * 1 
) t2 order by max_val desc

按顺序打印整数列的间隙和孤岛：

┌──────┬───────────┐ 
│ tick │ the_value │ 
├──────┼───────────┤ 
│ XYZ  │        -5 │ 
│ XYZ  │        -4 │ 
│ XYZ  │         0 │ 
│ XYZ  │         1 │ 
│ XYZ  │         2 │ 
│ XYZ  │        34 │ 
│ XYZ  │        35 │ 
│ XYZ  │        36 │ 
│ XYZ  │        37 │ 
│ XYZ  │        85 │ 
└──────┴───────────┘ 
┌──────┬──────────────┬─────────┬─────────┬───────────┐ 
│ tick │ island_width │ min_val │ max_val │ gap_width │ 
├──────┼──────────────┼─────────┼─────────┼───────────┤ 
│ XYZ  │            1 │      85 │      85 │        48 │ 
│ XYZ  │            4 │      34 │      37 │        32 │ 
│ XYZ  │            3 │       0 │       2 │         4 │ 
│ XYZ  │            2 │      -5 │      -4 │         ¤ │ 
└──────┴──────────────┴─────────┴─────────┴───────────┘

列island_width给出了连续数据的宽度。gap_width为您提供缺失数据的宽度。这允许你说："；让我看看岛与岛之间的空隙"；或"；给我看岛的大小和开始/停止位置"；