在LINQ中,左外部联接(Left Outer Join)是一种联接操作,它返回左边数据源中的所有记录,以及与右边数据源中匹配的记录。如果右边数据源中没有匹配的记录,那么对应的结果将包含空值。 左外部联接在以下情况下特别有用: 当需要获取左边数据源中的所有记录,无论是否有匹配的记录。
我们知道在SQL中一共有五种JOIN操作:INNER JOIN、LEFT OUTER JOIN、RIGHT OUTER JOIN、FULL OUTER JOIN、CROSS JOIN 1>先创建两个表Group、User,两表的关系是N:N CREATE TABLE [dbo].[Group]( [Id] [int] IDENTITY(1,1) NOT NULL, [GroupName] [nvarchar](50) NULL, CONSTRAINT [PK_Group] PRIMARY K...
var leftOuterJoin = from left in leftSet join right in rightSet on left.Key equals right.Key into temp from right in temp.DefaultIfEmpty() select new { Left = left, Right = right }; 在这个示例中,leftSet和rightSet是两个数据集,Key是用于连接它们的键。join子句将两个数据集连接在一起,in...
2、左连接(LEFT JOIN) //Sql: SELECT g.GroupName,u.UserName FROM GroupName g LEFT JOIN User u ON g.Id = u.GroupId //Linq to Sql: from g in Groups join u in Users on g.Id equals u.GroupId into Grp from grp in Grp.DefaultIfEmpty() select new { GroupName=g.GroupName, UserName...
LEFT OUTER JOIN [User_StudyRecord] AS t3 ON t6.UserID = t3.UserID AND t3.ResourceID = 1. 2. 3. 4. 5. 6. 7. 8. 9. 10. 11. 12. 13. 14. 15. 16. 当它被翻译成LINQ之后,是分页产生的结果,所以感觉更很乱了,呵呵,(LINQ在翻译SQL时,本来就够乱的,再一分页,用上row_number,更...
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] ...
VB SubMain() InnerJoinExample() LeftOuterJoinExample() CompositeKeyJoinExample() Console.ReadLine()EndSub 按F5 运行示例。 另请参阅 其他资源 培训 模块 采用T-SQL 通过 JOIN 合并多个表 - Training 采用T-SQL 通过 JOIN 合并多个表
默认情况下,GroupJoin 执行与左外部联接left outer join等效的操作。要获得内部联接inner join(从而排除没有购买的客户),您需要过滤 custPurchases: fromcincustomersjoinpinpurchasesonc.IDequalsp.CustomerIDintocustPurchaseswherecustPurchases.Any()select... ...
This limitation no longer exists: when StreamInsight encounters an unrecognized method (e.g. LeftOuterJoin in the above example) returning a stream definition, it will invoke the method to see what it returns, on the grounds that doing so may be better than failing....
This limitation no longer exists: when StreamInsight encounters an unrecognized method (e.g. LeftOuterJoin in the above example) returning a stream definition, it will invoke the method to see what it returns, on the grounds that doing so may be better than failing....