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linq to sql join

var q= from n in db.NewsModel join b in db.BigClassModel on n.BigClassID equals b.BigClassID join s in db.SmallClassModel on n.SmallClassID equals s.SmallClassID orderby n.AddTime descending select new { n.NewsID, n.BigClassID,...

}; 注意这里最后可以通过 y != null 来判断右值是否为空。 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 [...

var q= from n in db.NewsModel join b in db.BigClassModel on n.BigClassID equals b.BigClassID join s in db.SmallClassModel on n.SmallClassID equals s.SmallClassID orderby n.AddTime descending select new { n.NewsID, n.BigClassID,...

1.新建一个winform项目。 2.添加一个Linq to Sql 类,命名为Northwind 3.打开服务器资源管理器,将表拖动到linq to sql 类,实体类就由Vs生成了 4.实例化DataContext类 1 NorthwindDataContext dc = new NorthwindDataContext(); 5.下面就可以使...

sql = "select * from t where 1=1"; //姓名不为空就把姓名加入where条件 if (!string.IsNullOrEmpty(this.txtName.Text.Trim())) { sql = sql + string.Format(" and name like '%{0}%'", this.txtName.Text.Trim()); } //身份证号不为空就把身...

var result = from a in A表 join b in B表 on a.某字段 equals b.某字段 select new { a.XXX, b.XXX }; 或者 var result = from a in A表 from b in B表 where a.某字段 == b.某字段 select new { a.XXX, b.XXX };

--构造测试数据: 只作演示用 CREATE TABLE [dbo].[Tim_LinqTable]( [Id] int PRIMARY KEY IDENTITY(1,1) NOT NULL, [Name] [varchar](50) NOT NULL, [Parent] int NOT NULL, ) GO INSERT INTO [Tim_LinqTable] SELECT 'A',0 UNION ALL SELECT '...

是否是你正在编辑那个表的结构的同时来做查询啊?是否是你已打开了2个或更多个Access,而且其中有1个正在编辑那个表的结构呢?

假设 A 和 B 是两个集合, A要做外链接B, 连接条件A.SID=B.SID var result = from a in A join b in B on A.SID equals B.SID into G from g in G.DefaultIfEmpty() select new { ..... };

from a in db.table1 join b in db.table2 on a.field1=b.field2

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