在本文中，我们将详细介绍SQLServer：从分组依据中选择最后一个结果的各个方面，并为您提供关于sqlserver分组后取最新一条的相关解答，同时，我们也将为您带来关于linq分组依据并选择内部分组

在本文中，我们将详细介绍SQL Server：从分组依据中选择最后一个结果的各个方面，并为您提供关于sqlserver分组后取最新一条的相关解答，同时，我们也将为您带来关于linq分组依据并选择内部分组依据给出错误EFcore、MS Access SQL 从分组数据中选择 MAX、MySQL-选择不在分组依据中的列、php – 如何从mysql结果中选择第一个和最后一个数据行？的有用知识。

• SQL Server：从分组依据中选择最后一个结果（sqlserver分组后取最新一条）
• linq分组依据并选择内部分组依据给出错误EFcore
• MS Access SQL 从分组数据中选择 MAX
• MySQL-选择不在分组依据中的列
• php – 如何从mysql结果中选择第一个和最后一个数据行？

SQL Server：从分组依据中选择最后一个结果（sqlserver分组后取最新一条）

我正在尝试从2个相似的结果（最旧的结果）中检索最后一个结果

FromUser | ToUser | Message | DateUser1    | User2  | hi      | 01/01/2013 20:00User1    | User2  | hi later| 01/01/2013 21:00User5    | User2  | hi      | 01/01/2013 20:01User5    | User2  | hi later| 01/01/2013 21:01SELECT            CM.FromUser, CM.ToUser, CM.Message, CM.Date,     U.UserId, U.UserFullName, U.UserName, U.UserPhotoFROM    ConversationMessages AS CM INNER JOIN    Users AS U ON U.UserName = CM.FromUserWHERE    CM.ToUser = @userORDER BY     CM.Date DESC

它应先列出用户5嗨，然后再列出用户1嗨，然后再列出（用户5在日期上较新）。只有最后一行基本上按FromUser日期分组，然后按日期排序。我对sql没用，在这里尝试了许多建议，但没有任何工作

答案1

您想为此使用窗口函数，而不是group by：

select FromUser, ToUser, Message, [Date], UserId, UserFullName, UserName, UserPhotofrom (SELECT CM.FromUser, CM.ToUser, CM.Message, CM.Date, U.UserId,             U.UserFullName, U.UserName, U.UserPhoto,             row_number() over (partition by CM.FromUser, CM.ToUser order by [Date] desc) as seqnum      FROM ConversationMessages CM INNER JOIN           Users U           ON U.UserName = CM.FromUser      WHERE  CM.ToUser = @user     ) sWHERE seqnum = 1ORDER BY CM.Date DESC ;

linq分组依据并选择内部分组依据给出错误EFcore

这是我最能解决您的查询的问题。

var rslt =
(
    await
    (
        from d in db.statMonth.Include(f => f.MasterData)
        where d.m_turbine_id == IPAddress.Parse(id)
        where d.m_date >= frm
        group d by new { d.m_date.Month,d.m_date.Year } into g
        orderby g.Key.Month
        select new
        {
            Year = g.Key.Year,Date = g.Key.Month,Production = g.Sum(s => s.m_energy_prod),m_wind_speed = g.Average(s => s.m_wind_speed),Availability = g.Average(s => s.m_availability),Comments = g.Select(s => s.Comments).ToArray(),Countries = g.Select(i => i.Country).ToArray(),}
    )
    .ToListAsync()
)
.Select(g => new statisticsDaily
{
    Year = g.Year
    Date = CultureInfo.CurrentCulture.DateTimeFormat.GetMonthName(g.Date),Production = g.Production,m_wind_speed = g.m_wind_speed,Availability = g.Availability,Comments = String.Join(",",g.Comments),Countries = String.Join(",g.Countries),})
.ToList();

您可以检查一下现在遇到什么错误吗？

MS Access SQL 从分组数据中选择 MAX

SELECT DISTINCT
    dataset.CustomerId,dataset.ProductCode,dataset.LastDate
FROM
    dataset 
INNER JOIN (
SELECT
    ProductCode,MAX(LastDate) LastDate
FROM
    dataset
GROUP BY
    ProductCode
) last_purchased ON dataset.ProductCode = last_purchased.ProductCode AND
                    dataset.LastDate = last_purchased.LastDate

CustomerID = TheCustomerIDToFind    '' Number
ProductCode = TheProductCodeToFind  '' Text

LastDate = DMax("LastDate","YourTable","CustomerID = " & CustomerID & " And ProductCode = ''" & ProductCode & "''"

Select CustomerID,ProductCode,Max(LastDate)
From YourTable
Group By CustomerID,ProductCode

SELECT AVG(table1.col1), table1.personID, persons.col4
FROM table1 JOIN persons ON (table1.personID = persons.id)
GROUP BY table1.personID;

SELECT
     AVG(table_name.col1),AVG(table_name.col2),AVG(table_name.col3),table_name.personID,table_name.col4
FROM table_name
GROUP BY table_name.personID;

SELECT * from User LIMIT 1
UNION
SELECT * from User LIMIT 74,1

$result = MysqL_query('SELECT * from User');

MysqL_data_seek($result,1);
$row1 = MysqL_fetch_assoc($result);

MysqL_data_seek($result,75);
$row75 = MysqL_fetch_assoc($result);