1.sql语句: select * from Users u join Teachers t on u.UserID==t.TeacherID and u.Name=t.Name 2.linq写法: 1).方法一: 将多个字段的比较,new 一个对象进行比较: 注意:对象的属性名要保持一致: var userInfos = from u in db.Users join t in db.Teachers on new { u.UserID , u.Name } equals new { User
var a = from m in DbContext.Set<T1>() join q in DbContext.Set<T2>() on new { m.ID, Phone=m.Phone1 } equals new { q.ID, Phone=q.Phone2 } where m.Phone1 !=null select new { m.ID, m.Phone1 }; a = a.OrderBy(m => m.Phone1).Skip().Take(); SELECT
还是习惯先撸一段SQL * FROM User_Pic P AND P.Guid = R.UserPicGuid ORDER BY PicSize DESC 然后发现Linq中的join不能多条件... 结果找到解决方案如下 ; var pic = (from p in db.User_Pic join r in db.R_User_Pic on new { _guid = p.Guid, _id = ID } equals new { _guid = r.UserPicGuid, _id =
public class ObjectReflection { public static PropertyInfo[] GetPropertyInfos(Type type) { return type.GetProperties(BindingFlags.Public | BindingFlags.Instance); } public static void AutoMapping<S, T>(S s, T t) { // get source PropertyInfos Propert
linq中的contains条件 在sql查询语句中,in 在linq 中用contains,并且contains前面是数组,而后面是列名,如: SELECT distinct BH FROM cd where (LB = '身份') AND (LM IN ('合同工','临时工')) 转换成Linq 是这样的: 如果sf是变量,是在程序中根据用户选择的条件临时添加的,sf可以为空,也可不为空, 在程序中定义sf,在程序中赋值为:sf="合同工","临时工"
left join on +多条件与where区别 重点 先匹配,再筛选where条件. 本文将通过几个例子说明两者的差别. 1. 单个条件 select * from product a left join on product_details b on a.id = b.id 2. 条件写在on 与where区别 查询1: SELECT * FROM product LEFT JOIN product_details ON (product.id = product_details.id)
a left join b 时限制条件在on后, 相当于先筛选右连接表b的数据后,再进行数据连接.形成最终的集合. 这时不影响a表中相关字段的显示. SELECT T001W~WERKS, LGORT, LGOBE INTO TABLE @DATA(LT_T001W) FROM T001W LEFT JOIN T001L ON T001W~WERKS = T001L~WERKS AND T001L~WERKS LIKE '11%' WHERE T001W~WERKS LIKE '1%'. 执行
构造函数与原型对象的同名属性,实例会取哪一个? 看了下面的过程,再回忆JS高程3里关于这部分的示意图.实例my在new的时候,本身就获得了a属性,所以my.a是1,倘若在new的时候如果没有赋予a属性,则会从原型上搜索a属性,my.a是2.为什么有这个问题?因为在研究ES6和React中this的时候,碰到了这个易出错的地方. function A() { this.a = 1; //注释掉这句就从原型上获取了 } A.prototype.a = 2; var my = new A(); con
Linq Join Group by 时报Nullable object must have a value. 例如: from s in subject on ch.SubId equals s.SubId join gc in (from aq in question group aq by aq.ChapterId into gaq select new { Id = gaq.Key, Count = gaq.Count(), }) on s.QueId equals gc.Id into
作者按:虚拟函数的概念早就滚瓜烂熟了.但是今天面试发现:1.同名属性,2.同名普通函数,3.同名静态函数,是否被覆盖的问题.请看下面三个例子: 例子1:测试父类的属性是否存在和被完全覆盖class A{ public int i; A() { i=1; }}class B extends A{ public int i; B() { i=2; }}class C extends B{ public int i; C() { i=3; }}public class xx { public stat
var haveChange = from newScore in newScoreList join oldScore in oldScoreList on new{newScore.ExamId,newScore.StudentId,newScore.Subject,newScore.ClassId} equals new{oldScore.ExamId,oldScore.StudentId,oldScore.Subject,oldScore.ClassId} where newScore.
