Question

我正在尝试创建Linq，它执行与下面的SQL相同的连接：

select *
    from Table1
        inner join Table2 on Table1.ID = (select ID from Table2 where ID= 281026)

（我知道这样做是没有意义的，但我只是想知道加入背后的原则是否可行）

我到目前为止Linq：

from t1 in ctxt.Table1
     join t2 in ctxt.Table2
         on t1.ID equals new { ID = (from t2a in ctxt.Table2
                                     where t2a.ID == 281026 
                                     select t2a.ID) }
select t1;

然而我得到的错误是：

The type of one of the expressions in the join clause is incorrect. Type inference failed in the call to 'Join'.

t1.ID和t2a.ID都是整数。

有更好的方法吗？

Answer 1

                                 from t2a in ctxt.Table2
                                 where t2a.ID == 281026 
                                 select t2a.ID

这样做有什么意义？如果它返回任何内容，则此子查询将始终返回281026 ...

您的查询等同于：

 from t1 in ctxt.Table1
 join t2 in ctxt.Table2
     on t1.ID equals t2.ID
 where t2.ID == 281026
 select t1;

Answer 2

你在找这个吗？

from t1 in ctxt.Table1
join t2 in ctxt.Table2 on t1.ID equals 
    (from t2a in ctxt.Table2 
    where t2a.ID == 281026 
    select t2a.ID)
select t1;

Linq to Sql join with select

2 个答案: