SQL Oracle：如何对患者传输数据进行排序

Question

我希望你能帮我写下关于病房病人转移的查询。正如你们大多数人所知，患者可以从一个病房转移到另一个病房，也可以从床转移到同一个病房的另一张床，但对于这个查询，我只想 病房转移并且有每个不同单元中每次接送的首次到达和最后更新，并忽略任何床到床的接送，这里是一个例子：

PATIENT_ID  Start_Date   END_DATE   UNIT_NAME   BED_NUMBER
----------------------------------------------------------
1           01/01/2015   01/02/2015     A          1
1           01/02/2015   01/03/2015     A          2    
1           01/03/2015   01/03/2015     B          1
1           01/03/2015   01/04/2015     C          5
1           01/04/2015   01/06/2015     C          8
1           01/06/2015   01/07/2015     C          9
1           01/07/2015   01/08/2015     A          1

输出应该是：

PATIENT_ID  Start_Date   END_DATE     UNIT_NAME
------------------------------------------------
1           01/01/2015   01/03/2015      A
1           01/03/2015   01/03/2015      B
1           01/03/2015   01/07/2015      C
1           01/07/2015   01/08/2015      A

请注意，患者转移可以在同一天进行多次。

Answer 1

这是 gaps-and-islands problem. You can use Tabibitosan 的方法。完整参考 link 这个方法的解释。

SQL Fiddle

Oracle 11g R2 架构设置:

create table hospi(
    patien_id   number,
    start_date  date,
    end_date    date,
    unit_name   varchar2(1),
    bed_number  number
);

insert into hospi values(1, date'2015-01-01', date'2015-01-02',  'A',  1);
insert into hospi values(1, date'2015-01-02', date'2015-01-03',  'A',  2);
insert into hospi values(1, date'2015-01-03', date'2015-01-03',  'B',  1);
insert into hospi values(1, date'2015-01-03', date'2015-01-04',  'C',  5);
insert into hospi values(1, date'2015-01-04', date'2015-01-06',  'C',  8);
insert into hospi values(1, date'2015-01-06', date'2015-01-07',  'C',  9);
insert into hospi values(1, date'2015-01-07', date'2015-01-08',  'A',  1);
insert into hospi values(2, date'2015-01-07', date'2015-01-08',  'A',  1);
insert into hospi values(2, date'2015-01-08', date'2015-01-08',  'B',  1);
insert into hospi values(2, date'2015-01-08', date'2015-01-09',  'B',  1);

查询:

select
    patien_id,
    min(start_date)     start_date,
    max(end_date)       end_date,
    unit_name
from (
    select 
        patien_id,
        start_date,
        end_date,
        unit_name,
        row_number() over (partition by patien_id order by start_date, end_date) -
        row_number() over (partition by patien_id, unit_name order by start_date, end_date)     grp
    from hospi
)
group by
    patien_id,
    unit_name,
    grp
order by
    patien_id,
    start_date,
    end_date

Results:

| PATIEN_ID |                START_DATE |                  END_DATE | UNIT_NAME |
|-----------|---------------------------|---------------------------|-----------|
|         1 | January, 01 2015 00:00:00 | January, 03 2015 00:00:00 |         A |
|         1 | January, 03 2015 00:00:00 | January, 03 2015 00:00:00 |         B |
|         1 | January, 03 2015 00:00:00 | January, 07 2015 00:00:00 |         C |
|         1 | January, 07 2015 00:00:00 | January, 08 2015 00:00:00 |         A |
|         2 | January, 07 2015 00:00:00 | January, 08 2015 00:00:00 |         A |
|         2 | January, 08 2015 00:00:00 | January, 09 2015 00:00:00 |         B |

注意：如果start_date和end_date中不存储时间部分，且同一天单元间转账较多，则无法确定顺序发生转移的地方。

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