如何在Linq中的where條件中編寫快速子查詢

Question

我嘗試在linq條件條件下編寫子查詢。 但是，當我在sql server profiler中查看sql語法時，我的查詢看起來很復雜而且很長，並且在服務器中發生了超時錯誤。

我想編寫如下查詢。

SELECT 
T1.Id,
T2.Id,
DATEADD(HOUR, 
    ISNULL(
    (
        SELECT 
            MAX(T3.MaxHour) AS [MaxHour]
        FROM TABLE3 T3 WITH(NOLOCK)
        WHERE 
            T1.CategoryId=T3.CategoryId
    ),
    0),T1.EndDate
    ),
T1.StartDate 
FROM   
    TABLE1 T1 WITH(NOLOCK)    
LEFT OUTER JOIN TABLE2 T2 WITH(NOLOCK)  ON T1.Id=T2.Id  
WHERE
    DATEADD(HOUR, 
    ISNULL(
    (
        SELECT 
            MAX(T3.MaxHour) AS [MaxHour]
        FROM TABLE3 T3 WITH(NOLOCK)
        WHERE 
            T1.CategoryId=T3.CategoryId
    ),
    0),T1.EndDate
    ) 
    > '2014-11-05 00:00:00'
AND
    T1.StartDate < '2014-11-05 06:00:00'

我這樣寫我的linq表達式。

        var actualData = from T1 in _context.TABLE1
                         join T2 in _context.TABLE2 on T1.Id equals T2.Id into data
                         from x in data.DefaultIfEmpty()
                         where
                             EntityFunctions.AddHours(T1.EndDate,
                             (
                                (int?)((from T3 in _context.TABLE3
                                        where
                                             T3.CategoryId == T1.CategoryId
                                        select
                                            T3).Max(row => row.MaxHour))
                             ) ?? 0
                             ) >= '2014-11-05 00:00:00'
                             && T1.StartDate < '2014-11-05 06:00:00'

                         select
                             new 
                             {
                                 Id1 = T1.Id,
                                 Id2 = T2.Id,
                                 StartDate = T1.StartDate,
                                 EndDate =  EntityFunctions.AddHours(T1.EndDate,
                                    (
                                        (int?)((from T3 in _context.TABLE3
                                        where
                                             T3.CategoryId == T1.CategoryId
                                        select
                                            T3).Max(row => row.MaxHour))
                                    ) ?? 0
                                )

                             };

但是，我似乎不想在sql中看到它。

我如何用linq書寫？

謝謝。

Answer 1

嘗試：

    var actualData = from T1 in _context.TABLE1
                     join T2 in _context.TABLE2 on T1.Id equals T2.Id into data
                     from x in data.DefaultIfEmpty()

                     let endate = EntityFunctions.AddHours(T1.EndDate,
                         (
                            (
                                from T3 in _context.TABLE3
                                where T3.CategoryId == T1.CategoryId
                                select T3).Max(row => row.MaxHour)
                            )
                         ) ?? 0
                     )

                     where
                         enddate >= '2014-11-05 00:00:00'
                         && T1.StartDate < '2014-11-05 06:00:00'

                     select
                         new 
                         {
                             Id1 = T1.Id,
                             Id2 = T2.Id,
                             StartDate = T1.StartDate,
                             EndDate = enddate
                         };

而且我懷疑您可以將強制類型轉換為(int?) ，因為默認情況下max(int)返回int?