Linq實現左連接、右連接
阿新 • • 發佈：2019-03-14
nsq 連接 判斷 joins bsp left join fault insert tmp --一本錯誤的記錄
insert into Book values(‘錯誤時怎樣練成的‘,111)
--左連接
select s.name,b.name from student as s
left join Book as b on s.id=b.studentid
--右連接
select s.name,b.name from student as s
right join Book as b on s.id=b.studentid
要用Linq實現左連接，寫法如下
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//這裏主要第二個集合有可能為空。需要判斷
};
用Linq實現右連接，寫法如下
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實現左連接、右連接