我有一個查詢:Linq To SQL。如何防止使用應用運營商
var contactInfos = from person in persons
join tempDesiredCar in desiredCars on person.contact_id equals tempDesiredCar.groupEntity_id
into tempDesiredCars
from desiredCar in tempDesiredCars.DefaultIfEmpty()
select new {name = person.name, car = desiredCar.name};
此代碼轉換爲SQL:
SELECT [t1].[name], [t19].[name] AS [car]
FROM [dbo].[Person] AS [t1]
CROSS APPLY ((
SELECT NULL AS [EMPTY]
) AS [t6]
OUTER APPLY (
SELECT [t18].[name]
FROM (
SELECT [t17].[contact_id], [t17].[name]
FROM (
SELECT [t7].[contact_id], [t11].[name]
FROM [dbo].[DesiredCar] AS [t7]
INNER JOIN (
SELECT MAX([t9].[value]) AS [value]
FROM (
SELECT [t8].[id] AS [value], [t8].[contact_id]
FROM [dbo].[DesiredCar] AS [t8]
) AS [t9]
GROUP BY [t9].[contact_id]
) AS [t10] ON ([t7].[id]) = [t10].[value]
LEFT OUTER JOIN [dbo].[FamilyModel] AS [t11] ON [t11].[id] = [t7].[model]
WHERE [t7].[model] IS NOT NULL
UNION
SELECT [t12].[contact_id], [t16].[name]
FROM [dbo].[DesiredCar] AS [t12]
INNER JOIN (
SELECT MAX([t14].[value]) AS [value]
FROM (
SELECT [t13].[id] AS [value], [t13].[contact_id]
FROM [dbo].[DesiredCar] AS [t13]
) AS [t14]
GROUP BY [t14].[contact_id]
) AS [t15] ON ([t12].[id]) = [t15].[value]
LEFT OUTER JOIN [dbo].[CarBrand] AS [t16] ON [t16].[id] = [t12].[carBrand_id]
WHERE [t12].[carBrand_id] IS NOT NULL
) AS [t17]
) AS [t18]
where [t1].[contact_id] = [t18].[contact_id]
) AS [t19])
該代碼用途應用。如果替換通過左連接應用代碼運行更快在幾次。 如何強制Linq使用左連接生成代碼?
LINQ to SQL不是編寫SQL的「更好」方式,也不是它取代SQL。手動編寫這樣一個簡單的語句更容易,更快,並讓L2S從結果中創建新對象 –
此解決方案使自動重構不可用。 – Coder
請向我們展示完整的LINQ查詢... – usr