Как конвертировать сумму по разделу из T-SQL

У меня есть следующая таблица T-SQL, данные и запрос.

create table sampledata 
(
    name nvarchar(50),
    sampletime datetime,
    samplevalue decimal
);

insert into sampledata (name, sampletime, samplevalue) values
('ABC1235', cast('2016/01/01 10:00:00 AM' as datetime), 50.00),
('ABC1235', cast('2016/01/01 10:05:00 AM' as datetime), 50.00),
('ABC1235', cast('2016/01/01 10:10:00 AM' as datetime), 50.00),
('ABC1235', cast('2016/01/01 10:15:00 AM' as datetime), null),
('ABC1235', cast('2016/01/01 10:20:00 AM' as datetime), null),
('ABC1235', cast('2016/01/01 10:25:00 AM' as datetime), null),
('ABC1235', cast('2016/01/01 10:30:00 AM' as datetime), 50.00),
('ABC1235', cast('2016/01/01 10:35:00 AM' as datetime), 50.00),
('ABC1235', cast('2016/01/01 10:40:00 AM' as datetime), 50.00),
('ABC1235', cast('2016/01/01 10:45:00 AM' as datetime), 50.00),
('ABC1235', cast('2016/01/01 10:50:00 AM' as datetime), 50.00),
('ABC1235', cast('2016/01/01 10:55:00 AM' as datetime), 50.00),
('ABC1235', cast('2016/01/01 11:00:00 AM' as datetime), 50.00),
('ABC1235', cast('2016/01/01 11:05:00 AM' as datetime), null),
('ABC1235', cast('2016/01/01 11:10:00 AM' as datetime), null),
('ABC1235', cast('2016/01/01 11:15:00 AM' as datetime), 50.00),
('ABC1235', cast('2016/01/01 11:20:00 AM' as datetime), 50.00),
('ABC1235', cast('2016/01/01 11:25:00 AM' as datetime), 50.00),
('ABC1235', cast('2016/01/01 11:30:00 AM' as datetime), null),
('ABC1235', cast('2016/01/01 11:35:00 AM' as datetime), 50.00),
('ABC1235', cast('2016/01/01 11:40:00 AM' as datetime), 50.00),
('ABC1235', cast('2016/01/01 11:45:00 AM' as datetime), 50.00),
('ABC1235', cast('2016/01/01 11:50:00 AM' as datetime), null),
('ABC1235', cast('2016/01/01 11:55:00 AM' as datetime), null),
('ABC1235', cast('2016/01/01 12:00:00 PM' as datetime), 50.00),
('ABC1235', cast('2016/01/01 12:05:00 PM' as datetime), null),
('ABC1235', cast('2016/01/01 12:10:00 PM' as datetime), null),
('ABC1235', cast('2016/01/01 12:15:00 PM' as datetime), null),
('ABC1235', cast('2016/01/01 12:20:00 PM' as datetime), null),
('ABC1235', cast('2016/01/01 12:25:00 PM' as datetime), null),
('ABC1235', cast('2016/01/01 12:30:00 PM' as datetime), null)
('ZYA4567', cast('2016/01/01 10:00:00 AM' as datetime), 50.00),
('ZYA4567', cast('2016/01/01 10:05:00 AM' as datetime), 50.00),
('ZYA4567', cast('2016/01/01 10:10:00 AM' as datetime), 50.00),
('ZYA4567', cast('2016/01/01 10:15:00 AM' as datetime), null),
('ZYA4567', cast('2016/01/01 10:20:00 AM' as datetime), null),
('ZYA4567', cast('2016/01/01 10:25:00 AM' as datetime), null),
('ZYA4567', cast('2016/01/01 10:30:00 AM' as datetime), null),
('ZYA4567', cast('2016/01/01 10:35:00 AM' as datetime), 50.00),
('ZYA4567', cast('2016/01/01 10:40:00 AM' as datetime), 50.00),
('ZYA4567', cast('2016/01/01 10:45:00 AM' as datetime), 50.00),
('ZYA4567', cast('2016/01/01 10:50:00 AM' as datetime), 50.00),
('ZYA4567', cast('2016/01/01 10:55:00 AM' as datetime), 50.00),
('ZYA4567', cast('2016/01/01 11:00:00 AM' as datetime), 50.00),
('ZYA4567', cast('2016/01/01 11:05:00 AM' as datetime), null),
('ZYA4567', cast('2016/01/01 11:10:00 AM' as datetime), null),
('ZYA4567', cast('2016/01/01 11:15:00 AM' as datetime), 50.00),
('ZYA4567', cast('2016/01/01 11:20:00 AM' as datetime), 50.00),
('ZYA4567', cast('2016/01/01 11:25:00 AM' as datetime), 50.00),
('ZYA4567', cast('2016/01/01 11:30:00 AM' as datetime), null),
('ZYA4567', cast('2016/01/01 11:35:00 AM' as datetime), 50.00),
('ZYA4567', cast('2016/01/01 11:40:00 AM' as datetime), 50.00),
('ZYA4567', cast('2016/01/01 11:45:00 AM' as datetime), 50.00),
('ZYA4567', cast('2016/01/01 11:50:00 AM' as datetime), null),
('ZYA4567', cast('2016/01/01 11:55:00 AM' as datetime), null),
('ZYA4567', cast('2016/01/01 12:00:00 PM' as datetime), 50.00),
('ZYA4567', cast('2016/01/01 12:05:00 PM' as datetime), null),
('ZYA4567', cast('2016/01/01 12:10:00 PM' as datetime), null),
('ZYA4567', cast('2016/01/01 12:15:00 PM' as datetime), null),
('ZYA4567', cast('2016/01/01 12:20:00 PM' as datetime), null),
('ZYA4567', cast('2016/01/01 12:25:00 PM' as datetime), 40.00),
('ZYA4567', cast('2016/01/01 12:30:00 PM' as datetime), 50.00)

Запрос:

select 
    name, 
    sampletime,
    samplevalue,
sum(case when samplevalue is null then 0 else 1 end) 
over(partition by name order by sampletime) 
* case when samplevalue is null then 1 else 0 end as block
from sampledata

Мне нужно преобразовать его в LINQ.

Я решил разбить его на два этапа (мой фактический запрос более сложен, содержит объединения и предложения where, чем в этом примере)

var list = (from s in db.sampledata).ToList();

Теперь я не уверен, как это сделать

sum(case when samplevalue is null then 0 else 1 end) 
over(partition by name order by sampletime) 
* case when samplevalue is null then 1 else 0 end as block
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1 ответ

Решение

Вы не можете сделать это с помощью LinQToSQL, потому что нет прямого преобразования в SQL over partition ограничение от Linq.

Но вы можете сделать это на стороне клиента, я предлагаю вам так:

int i = 0; //we need this for closure
var list = db.sampledata
    .OrderBy(x => x.name) 
    .ThenBy(x => x.sampletime) //order your data like partition function do
    .ToList() //get all from DB to server memory
    .Select(x =>
    {
        int block = 0; //logic of your block calculation
        if (x.samplevalue.HasValue)
            i++;
        else
            block = i;
        //return your full collection
        return new { 
                      name = x.name, 
                      sampletime = x.sampletime, 
                      samplevalue = x.samplevalue, 
                      block = block 
                   };
    });

Как видите, логика сортировки и выбора будет на стороне БД, но вычисляемое поле block будет на стороне LinQ.

Другой способ, который может вас заинтересовать, - обернуть ваш запрос T-SQL хранимой процедурой или хранимой функцией и сопоставить его с вашим LinQToSQL. DataContext так что вы можете назвать это.

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