LINQ到SQL - 分组由小时 [英] LINQ to SQL - Grouping by hours

问题描述

我怎么能一个LINQ to SQL查询时所考虑到列类型为日期时间？组结果

How can I group result of a LINQ to SQL query by hours considering that the column type is DateTime?

推荐答案

下面是技术小时（上下文更少）的解决方案。

Here's a solution for technical hours (context-less).

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

产生这样的：

Which generates this:

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]

---

下面是营业时间（上下文FUL）的解决方案。

---

Here's a solution for business hours (context-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});

产生这样的：

Which generates this:

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]

---

唉 - 这BIGINT /浮点/毫秒的东西是丑陋和难以核实。我preFER做加法回客户端：

---

Ugh - that bigint/float/milliseconds stuff is ugly and hard to verify. I prefer doing the addition back on the client side:

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});

产生这样的：

Which generates this:

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]

---

和这里做contextful小时的第三条道路。这一个是非常C＃友好，但有串逻辑数据库（呸）。

---

And here's a third way of doing the contextful hours. This one is very c# friendly, but there's string logic in the database (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) });

生成

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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