c.ContactName, OrderCount = orders.Count () }; 说明:在一对多关系中,左边是1,它每条记录为c(from c in db.Customers),右边是Many,其每条记录叫做o ( join o in db.Orders ),每对应左边的一个c,就会有一组o,那这一组o,就叫做orders, 也就是说,我们把一组o命名为orders,这就是into用途。这也就...
左连接(两张表) 1varlist =fromaindb.Specialty2join bindb.School on a.Specialty_School_id equals b.School_id into c3fromdinc.DefaultIfEmpty()4selectnew{5a.Specialty_id,6a.Specialty_name,7a.Specialty_mark,8a.Specialty_type,9a.Specialty_School_id,10d.School_id,11d.School_name,12d.School_mark,...
像上面所说的,没有 join 和 into,被翻译成 SelectMany,同时有 join 和 into 时,那么就被翻译为 GroupJoin。在这里 into 的 概念是对其结果进行重新命名。 1.双向联接(Two way join): 此 示例显式联接两个表并从这两个表投影出结果: var q = from c in db.Customers join o in db.Orderson c.Custom...
//Conventional LINQ var commonData = from t1 in dc.TableA join t2 in dc.TableB on new { t1.Column1, t1.Column2 } equals new { t2.Column1,t2.Column2} select t1; //LINQ Extensions var commonData1 = dc.TableA.Join(dc.TableB, c1 => new { c1.Column1, c1.Column2 }, c2 =...
1:LINQ TO SQL中的join,如果带有into,可以提前对表进行过滤条件的操作,而不用等到两表进行迪卡尔积产生虚似表后再进行join on的条件过滤。 Code from c in Customers join p in Purchases.Where (p2 => p2.Price > 1000) on equals p.CustomerID into custPurchases where custPurchases.Any() select new...
C的LINQ-SQL支持在JOIN中使用多个IN操作符吗? 在C#中,对于LINQ-SQL的JOIN查询使用多个IN子句,可以通过使用Contains方法和Any方法来实现。 首先,JOIN查询是用于合并两个或多个数据源的操作。而IN子句用于在WHERE条件中指定一个字段值在给定列表中的匹配。在LINQ中,JOIN操作可以通过使用join关键字和on子句来实现,而I...
是指将SQL语句中的左连接子查询转换为LINQ查询语句的过程。 在SQL中,左连接子查询是通过使用LEFT JOIN关键字将两个或多个表连接起来,并在连接条件不满足时返回左表中的所有记录。而LINQ是一种用于查询和操作数据的编程语言集成查询(Language Integrated Query)。 在LINQ中,可以使用LINQ to SQL或者LINQ to Entities...
[SQL Server Native Client 11.0]Connection is busy with results for another command [closed] [win 10, c#] Interop - Generic way to know if a window is Minimized, Maximized or Normal? [Y/N] Prompt C# \r\n not working! \t is not working but \n does #C code to Read the sectors on...
A couple of weeks ago, I posted some code to use LINQ to query tables in an Excel spreadsheet. Because you can query databases using LINQ to SQL, you can write code to query a database and do a join with data in an Excel spreadsheet. This can enable some interesting scenarios – let...
NoSQL SELECT*FROMFamilies fJOINcINf.childrenWHEREc.familyName ="Jeff" 嵌套,示例 3: LINQ Lambda 表达式 C# input.SelectMany(family => family.children.Where( child => child.familyName == family.parents[0].familyName)); NoSQL NoSQL SELECT*FROMFamilies fJOINcINf.childrenWHEREc.familyName = f....