左外连接(Left Outer Join)是一种数据库查询操作,它返回左表中所有记录的数据,即使右表中没有匹配的记录。在LINQ to SQL中,左外连接可以使用DefaultIfEmpty()方法来实现。 以下是一个使用LINQ to SQL实现左外连接的示例代码: 代码语言:csharp 复制 var leftOuterJoinQuery = from left in
[t0].[QuantityPerUnit],[t0].[UnitPrice], [t0].[UnitsInStock], [t0].[UnitsOnOrder],[t0].[ReorderLevel], [t0].[Discontinued] FROM [dbo].[Products] AS [t0] LEFT OUTER JOIN [dbo].[Suppliers] AS [t1] ON [t1].[SupplierID] = [t0].[SupplierID] WHERE ([t1].[Country] =...
Linq To SQL LEFT OUTER JOIN (Left Join) SQL: SELECT [t0].[ProductName], [t1].[TotalPrice] AS [TotalPrice] FROM [Product] AS [t0] LEFT OUTER JOIN [OrderDetail] AS [t1] ON [t0].[ProductID]=[t1].[ProductID] Linq Query:frompinProducts join odinOrderDetails on p.ProductID equals ...
3.左外部联接(Left Outer Join): 此示例说明如何通过使用 此示例说明如何通过使用 DefaultIfEmpty()获取左外部联接。在雇员没有订单时,DefaultIfEmpty()方 法返回 null: var q = from e in db.Employees join o in db.Orders on e equals o.Employeeinto ords from o in ords.DefaultIfEmpty() select new {...
Linq to sql 中如何进行 left join 可以用 into 语法,配合 DefaultIfEmpty() 方法加载右侧表中的空值。 例子: var query = from r in db.Roles join sr in ( from ss in db.StaffInRoles where ss.StaffId == staffId select ss...
这个 Linq to sql 语句生成的对应 SQL 为：exec sp_executesql N'SELECT [t0].[Id] AS [RoleId], [t0].[Name] AS [RoleName],(CASEWHEN [t2].[test] IS NOT NULL THEN 1ELSE 0END) AS [IsSet]FROM [Role] AS [t0]LEFT OUTER JOIN (SELECT 1 AS [test], [t1].[Staff...
对应的SQL:SELECT [t0].[Name], [t1].[Description] AS [Description], [t1].[Price] AS [Price]FROM [Customer] AS [t0]LEFT OUTER JOIN [Purchase] AS [t1] ON ([t1].[Price] > @p0) AND ([t1].[CustomerID] = [t0].[ID]) 此时上面的语句还是标准的LEFT OUT JOIN,如果我们改变下条件的...
这个Linqtosql语句生成的对应SQL为: execsp_executesqlN'SELECT[t0].[Id]AS[RoleId],[t0].[Name]AS[RoleName], (CASE WHEN[t2].[test]ISNOTNULLTHEN1 ELSE0 END)AS[IsSet] FROM[Role]AS[t0] LEFTOUTERJOIN( SELECT1AS[test],[t1].[StaffId],[t1].[RoleId] ...
[t0].[Discontinued]FROM[dbo].[Products]AS[t0]LEFT OUTER JOIN[dbo].[Suppliers]AS[t1]ON[t1].[SupplierID] = [t0].[SupplierID]WHERE([t1].[Country] = @p0)AND([t0].[UnitsInStock] = @p1)-- @p0: Input NVarChar (Size = 3; Prec = 0; Scale = 0) [USA] ...
SQL中常见的连接查询有: left join: 左连接,返回左表中所有的记录以及右表中连接字段相等的记录。 right join: 右连接,返回右表中所有的记录以及左表中连接字段相等的记录。 inner join: 内连接,又叫等值连接,只返回两个表中连接字段相等的行。 full join: 外连接,返回两个表中的行:left join + right join...