本文转自:https://stackoverflow.com/questions/530925/linq-using-inner-join-group-and-sum SELECT T1.Column1, T1.Column2, SUM(T3.Column1) AS Amount FROM T1 INNER JOIN T2 ON T1.T1ID = T2.T1ID INNER JOIN T3 ON T2.T3ID = T3.T3ID GROUP BY T1.Column1, T1.Column2
LINQ查询表达式---------group子句 LINQ表达式必须以from子句开头,以select或group子句结束.使用guoup子句来返回元素分组后的结果.group 子句返回一个 IGrouping<TKey, TElement> 对象序列(实质上是列表的列表).TKey是键的对象类型,在用于group子句的时候,它一般用于存储分组的键值:TElement是指的对象类型,用于存储分组的结果. class Program { public class PerInfo { publi
现有如下需求,要求统计int数组中每个整数的个数: ,,,,,,,,,,,, }; var linq = from item in arrInt group item by item into g//注意这里的into g,这里必须为g 表示范围变量IGrouping<int,int> select new {key=g.Key,value=g.Count() };//这里选择了整数的值为key,个数为值的匿名对象
需求是需要统计数据库中表某一列的总数量,同时以List的形式返回到UI层. Linq to SQL中的Group by用法如下: IList<Unit.HandleCountClass> result; result = (from a in db.handleinfo_users group a by a.han_Server into g select new HandleCountClass { type = g.Key, Handlecount = g.Count() }).ToLis
Group By/Having操作符 适用场景:分组数据,为我们查找数据缩小范围. 说明:分配并返回对传入参数进行分组操作后的可枚举对象.分组:延迟 1.简单形式: var q = from p in db.Products group p by p.CategoryID into g select g; 语句描述:使用Group By按CategoryID划分产品. 说明:from p in db.Products 表示从表中将产品对象取出来.group p by p.CategoryID i
在sql中,如果有group by,那么select的字段只能包含分组内容,或者count.sum.avg这些统计字段. 但在linq里面,是:group 你想要什么字段 by 分组字段 比如: var q = from p in db.Products group p by p.CategoryID into g select g; 实际应用中,多表多字段参与分组比较常见: from a in TableA join b in TableB on a.Id equals b.aId || b.
1. 简单形式 var expr = from p in context.Products group p by p.CategoryID into g select g; foreach (var item in expr) { Console.WriteLine(item.Key); foreach (var p in item) { Console.WriteLine("{0}-{1}", p.ProductID, p.ProductName); } } SELECT [Proj
场景:查询所有A表的数据,并且关联B表,再数据集中插入一个COUNT列.该列的数据是B表的COUNT 扩展:假设join的表数据为空,但我任然要把所有表A的数据取出来,那就用LEFT JOIN SELECT * FROM question AS A JOIN (SELECT question_id, COUNT(*) AS COUNT FROM visitor GROUP BY question_id) AS C ON A.id = C.question_id
表一: 表二: 已知表一的List,想得到表二的结果: var query = from c in t.AsEnumerable() group c by new { pingming = c.Field<string>("品名"), guige = c.Field<string>("规格") } into s select new { pingming = s.Select(p => p.Field<string>(&qu
//Line to Sql 写法 var data = (from a in Items group a by new { a.GroupId, a.Id } into b //orderby new ComparerItem() { GroupId = b.Key.GroupId, Id = b.Key.Id } descending .where(o => o.Id>1000) select new { GroupId = b.Key.GroupId, Id = b.Key.Id, Cou
CreationTime是DateTime类型 group by 年/月/日/小时 group by 年 (from d in YourData.OrderBy(x => x.CreationTime) group d by new { time = new { d.CreationTime.Year } } into g select new { AverageValue = g.Average(p => p.Value), CreationTimeStr = g.Key.time.Year
直接上代码: List<Student> ss = new List<Student>(); Student ss1 = , Age = , Name = " }; Student ss2 = , Age = , Name = " }; Student ss3 = , Age = , Name = " }; Student ss4 = , Age = , Name = " }; Student ss5 = , Age = , Name = &
问题: 学生表,班级表,我要班级下面学生 A表,字段:AID,CLASSB表,字段 :BID,BNAME,AIDA表数据1 班级12 班级2B表数据1 学生1 12 学生2 1 3 学生3 24 学生4 2我想得到CLASS NAME班级1 学生1,学生2班级2 学生3,学生4这样怎么联合? 答案: namespace ConsoleApplication1 { public class A { public int AID { get; set; } public string Class {
拥有476550数据的一张数据表.使用其中的某个字段分组,然后按该字段进行排序.该需求分别使用LinQ to SQL和non-LinQ的方式实现,然后来看一下performance对比. LinQ way from p in context.Part_Part group p by p.FunctionGroup into groupedPs orderby groupedPs.Key select groupedPs LinQ way for group non-LinQ way var re
本文转载自:http://www.cnblogs.com/sydeveloper/archive/2013/03/29/2988669.html 1.用两层循环计算,前提条件是数据已经按分组的列排好序的. DataTable dt = new DataTable(); dt.Columns.AddRange(new DataColumn[] { new DataColumn("name", typeof(string)), new DataColumn("sex",