--一本错误的记录
insert into Book values(‘错误时怎样练成的‘,111)
--左连接
select s.name,b.name from student as s
left join Book as b on s.id=b.studentid
--右连接
select s.name,b.name from student as s
right join Book as b on s.id=b.studentid
要用Linq实现左连接，写法如下
DataClasses1DataContext db = new DataClasses1DataContext();
var leftJoinSql = from student in db.Student
join book in db.Book on student.ID equals book.StudentID into temp
from tt in temp.DefaultIfEmpty()
select new
{
sname= student.Name,
bname = tt==null?"":tt.Name//这里主要第二个集合有可能为空。需要判断
};
用Linq实现右连接，写法如下
DataClasses1DataContext db=new DataClasses1DataContext();
var rightJoinSql = from book in db.Book
join stu in db.Student on book.StudentID equals stu.ID into joinTemp
from tmp in joinTemp.DefaultIfEmpty()
select new {
sname=tmp==null?"":tmp.Name,
bname=book.Name
};
Linq实现左连接、右连接
原文：https://www.cnblogs.com/Little-Sky/p/10530394.html
