Oracle query that count connections by minute with start and end times provided

数据结构类似
SQL> select * from t;

B E N

----------------- ----------------- --------------------

20150106 01:00:02 20150106 01:00:42 A

20150106 01:00:02 20150106 01:00:12 B

20150106 02:01:02 20150106 01:10:03 C

20150106 02:01:07 20150106 02:01:08 D

20150106 02:00:01 20150106 02:00:02 E

20150106 01:00:03 20150106 01:00:07 F

6 rows selected.

数据表定义
SQL> @desc t

Name Null? Type

------------------------------- -------- ----------------------------

1 B DATE

2 E DATE

3 N VARCHAR2(10)

需求抽象
以分钟为单位统计指定天每分钟内N的个数。

思路：
1、每天1440分钟，构造全天的分钟集合

[align=left]SELECT to_date('20150106 00:00:00' , 'yyyy-mm-dd hh24:mi:ss') +[/align]
[align=left] numtodsinterval (level , 'minute') dt[/align]
[align=left] FROM dual[/align]
[align=left] CONNECT BY level <= 24 * 60[/align]

[align=left] [/align]
[align=left]2、左外连接，条件 dt >= begin and dt < end + 1[/align]
[align=left] [/align]
[align=left]3、需要截取t.begin 和 t.end到分钟[/align]
[align=left]对于begin , trunc(begin,'mi')[/align]
[align=left]对于end , trunc(end+ numtodsinterval(1, 'minute'),'mi')) // trunc( end + 1 ,[format])[/align]
[align=left] [/align]
[align=left]4、按分钟聚合统计[/align]
[align=left] [/align]
[align=left] [/align]
[align=left]结果[/align]

[align=left]WITH each_minute AS[/align]
[align=left] ( SELECT to_date( '20150106 00:00:00' , 'yyyy-mm-dd hh24:mi:ss' ) +[/align]
[align=left] numtodsinterval (level , 'minute') dt[/align]
[align=left] FROM dual[/align]
[align=left] CONNECT BY level <= 24 * 60 )[/align]
[align=left]SELECT trunc (em.dt, 'mi') d, count (t.n) cnt[/align]
[align=left] FROM each_minute em[/align]
[align=left] LEFT OUTER JOIN t[/align]
[align=left] ON (em.dt >= trunc (t.b, 'mi') AND em.dt < trunc (t.e+ numtodsinterval (1 , 'minute'), 'mi' ))[/align]
[align=left]group by trunc(em.dt, 'mi' )[/align]
[align=left]order by 1;[/align]
[align=left] [/align]
[align=left]简单测试[/align]
SQL> WITH each_minute AS

2 (SELECT to_date('20150106 00:00:00', 'yyyy-mm-dd hh24:mi:ss') +

3 numtodsinterval(level, 'minute') dt

4 FROM dual

5 CONNECT BY level <= 24 * 60)

6 SELECT trunc(em.dt, 'mi') d, count(t.n) cnt

7 FROM each_minute em

8 LEFT OUTER JOIN t

9 ON (em.dt >= trunc(t.b, 'mi') AND

10 em.dt < trunc(t.e + numtodsinterval(1, 'minute'), 'mi'))

11 where t.n is not null -- no need for 1440,just for test.

12 group by trunc(em.dt, 'mi')

13 order by 1;

D CNT

----------------- ----------

20150106 01:00:00 3

20150106 02:00:00 1

20150106 02:01:00 1