/**************OrderBy ，Groupby练习*******************/
//按学生的总分数按降序排列排序
var list = from s in ctx.T_Student
join c in ctx.T_Score
on s.stuNumber
equals c.stuNumber
into temp
from t in temp
orderby temp.Sum(k => k.score) descending
select new {
stuName = s.stuName,
scoreSum = temp.Sum(k=>k.score)
};
//对学生的年龄和姓名进行排序
var list1 = from s in ctx.T_Student
orderby s.stuSex,s.stuName descending
select s;
//对于上边的可以用lambda进行简化
var list2 = ctx.T_Student.OrderBy(s => s.stuAge).ThenBy(k=>k.stuName);
//也可以用连续的orderBy进行排序，不过级联方式是逆序，上边的list2可以这样表示
var list3 = ctx.T_Student.OrderBy(s => s.stuName).OrderBy(k=>k.stuAge);
//对orderby排序要注意的地方是只能对基本数据类型进行排序，不能对类型，以及匿名类进行排序，否则的话会抛异常
//每门课程分数最高的分数，并按课程号进行排序
var list4 = from s in ctx.T_Score
group s by s.courceNumber
into g
orderby g.Key
select new
{
courceNumber = g.Key,
coreForCourse = from f in g
where f.score == g.Max(n => n.score)
select f
};
//下面着重对groupby进行案列练习,对分数按课程号进行分组
var list5 = from s in ctx.T_Score
group s by s.courceNumber
into temp1
select temp1;
//每门课程的最高分数
var list6 = from s in ctx.T_Score
group s by s.courceNumber
into temp1
select new {
courseNumber = temp1.Key,
maxCourece = temp1.Max(k=>k.score)
};
//分组的条件也可以是自定义的表达式，如下
var list7 = from s in ctx.T_Score
group s by s.score + 10
into g
select g;
//也可以对多列进行分组
var list8 = from s in ctx.T_Score
group s by new
{
s.courceNumber,
s.stuNumber
} into g
select new {
g.Key,
g
};