LINQ to SQL-группировка по часам

Как я могу сгруппировать результат запроса LINQ to SQL по часам, учитывая, что тип столбца-DateTime?

11
.net linq linq-to-sql sql

1 ответов

вот решение для технических часов (без контекста).

var query = myDC.Orders
    .GroupBy(x => x.OrderDate.Hour)
    .Select(g => new {
        Hour = g.Key,
        Amount = g.Sum(x => x.OrderAmount)
    });

который генерирует этот:

SELECT SUM([t1].[OrderAmount]) AS [Amount], [t1].[value] AS [Hour]
FROM (
    SELECT DATEPART(Hour, [t0].[OrderDate]) AS [value], [t0].[OrderAmount]
    FROM [dbo].[Orders] AS [t0]
    ) AS [t1]
GROUP BY [t1].[value]

вот решение для рабочих часов (контекст-ful).

DateTime zeroDate = new DateTime(2008, 1, 1);

var query = myDC.Orders
    .GroupBy(x => System.Data.Linq.SqlClient.SqlMethods.DateDiffHour(zeroDate, x.OrderDate)
    )
    .Select(g => new { Hours = g.Key, Amount = g.Sum(x => x.OrderAmount) })
    .Select(x => new { Hour = zeroDate.AddHours(x.Hours), Amount = x.Amount});

который генерирует этот:

SELECT DATEADD(ms, (CONVERT(BigInt,(CONVERT(Float,[t2].[value2])) * 3600000)) % 86400000, DATEADD(day, (CONVERT(BigInt,(CONVERT(Float,[t2].[value2])) * 3600000)) / 86400000, @p1)) AS [Hour], [t2].[value] AS [Amount]
FROM (
    SELECT SUM([t1].[OrderAmount]) AS [value], [t1].[value] AS [value2]
    FROM (
        SELECT DATEDIFF(Hour, @p0, [t0].[OrderDate]) AS [value], [t0].[OrderAmount]
        FROM [dbo].[Orders] AS [t0]
        ) AS [t1]
    GROUP BY [t1].[value]
    ) AS [t2]

тьфу - этот материал bigint/float/milliseconds уродлив и трудно проверить. Я предпочитаю делать добавление обратно на стороне клиента:

var results = myDC.Orders
    .GroupBy(x => System.Data.Linq.SqlClient.SqlMethods.DateDiffHour(zeroDate, x.OrderDate)
    )
    .Select(g => new { Hours = g.Key, Amount = g.Sum(x => x.OrderAmount) })
    .ToList()
    .Select(x => new { Hour = zeroDate.AddHours(x.Hours), Amount = x.Amount});

который генерирует это:

SELECT SUM([t1].[OrderAmount]) AS [Amount], [t1].[value] AS [Hours]
FROM (
    SELECT DATEDIFF(Hour, @p0, [t0].[OrderDate]) AS [value], [t0].[OrderAmount]
    FROM [dbo].[Orders] AS [t0]
    ) AS [t1]
GROUP BY [t1].[value]

и вот третий способ делать contextful часов. Это очень удобно для c#, но в базе данных есть строковая логика (yuck).

var query = myDC.Orders
    .GroupBy(x => new DateTime(x.OrderDate.Year, x.OrderDate.Month, x.OrderDate.Day, x.OrderDate.Hour, 0, 0))
    .Select(g => new { Hour = g.Key, Amount = g.Sum(x => x.OrderAmount) });

который генерирует

SELECT SUM([t1].[OrderAmount]) AS [Amount], [t1].[value] AS [Hour]
FROM (
    SELECT CONVERT(DATETIME, (CONVERT(NCHAR(4), DATEPART(Year, [t0].[OrderDate])) + ('-' + (CONVERT(NCHAR(2), DATEPART(Month, [t0].[OrderDate])) + ('-' + CONVERT(NCHAR(2), DATEPART(Day, [t0].[OrderDate])))))) + (' ' + (CONVERT(NCHAR(2), DATEPART(Hour, [t0].[OrderDate])) + (':' + (CONVERT(NCHAR(2), @p0) + (':' + CONVERT(NCHAR(2), @p1)))))), 120) AS [value], [t0].[OrderAmount]
    FROM [dbo].[Orders] AS [t0]
    ) AS [t1]
GROUP BY [t1].[value]
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