使用LINQ模拟SQL Server 2012滞后窗口功能 [英] Emulating SQL Server 2012 Lag Window function with LINQ

问题描述

我有一些示例数据，如下所示:(我没有SQL Server 2012)

I've got some sample data that look like: ( I don't have SQL Server 2012)

create table #base
(pat_id int
,admission_date date
,discharge_date date
)
go
insert into #base
values
(1, '2007-01-04',   '2007-01-04'),
(1, '2007-01-10',   '2007-01-10'),
(1, '2007-01-11',   '2007-01-11'),
(1, '2007-01-18',   '2007-01-18'),
(1, '2007-01-24',   '2007-01-24'),
(1, '2008-01-25',   '2008-01-26'),
(2, '2007-02-01',   '2007-02-01'),
(2, '2007-02-06',   '2007-02-06'),
(2, '2007-02-07',   '2007-02-07'),
(2, '2007-02-08',   '2007-02-08')

这是我想用LINQ模拟的SQL查询

Here's the SQL query I wish to emulate with LINQ

;with cte 
as
(
    select   pat_id
            ,admission_date
            ,discharge_date
            ,ROW_NUMBER() over(partition by pat_id order by admission_date asc) as rn
    from #base
)
select   firstCte.pat_id
        ,firstCte.discharge_date as firstAdmitReference
        ,secondCte.admission_date as dischargeReference
        ,case when DATEDIFF(DAY,firstCte.discharge_date,secondCte.admission_date) <= 30 then 1 else 0 end Readmit
from cte as firstCte
inner join cte as secondCte
      on firstCte.pat_id = secondCte.pat_id
where firstCte.rn = secondCte.rn -1 

以下是该查询的结果:

create table #readmit_data
( pat_id int
 ,admission_date date
 ,discharge_date date
 ,within_x_days int
 )
insert into #readmit_data(pat_id,admission_date,discharge_date,within_x_days)
values

(1, '2007-01-04',   '2007-01-10',   1),
(1, '2007-01-10',   '2007-01-11',   1),
(1, '2007-01-11',   '2007-01-18',   1),
(1, '2007-01-18',   '2007-01-24',   1),
(1, '2007-01-24',   '2008-01-25',   0),
(2, '2007-02-01',   '2007-02-06',   1),
(2, '2007-02-06',   '2007-02-07',   1),
(2, '2007-02-07',   '2007-02-08',   1)

在此结果集中，数据的基本格式为

In this result set the basic format for the data is

patient ID dischargeDate nextVisitAdmitDate

within_x_days列中的

1表示患者在上一次出院30天后已再次入院.理想情况下，30将是用户输入的变量.

A 1 in the within_x_days column indicates that a patient had a readmission with 30 days of their last discharge. Ideally, 30 will be a variable entered in by the user.

LINQ中可以使用哪种构造?

What sort of construct in LINQ is there available for doing this?

推荐答案

到LINQ的窗口是.NET扩展功能库

Window To LINQ is a library of extension functions for .NET

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