meid,十大整形医院,南昌绿湖豪城
--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
};
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