具有多个OR条件的EF核心连接

Question

我想将这个sql查询转换为linq：

select * from  A a
join B b on (    (a.level1= b.PerimeterID and  b.PerimeterLevelID = 1)
              OR (a.level2= b.PerimeterID and  b.PerimeterLevelID = 2)
              OR (a.level3= b.PerimeterID and  b.PerimeterLevelID = 3)
            )

我试过的是：

from a in A
join b in B on new {PerimeterID = a.level1, PerimeterLevelID = 1 } equals new { b.PerimeterID, b.PerimeterLevelID }
where (a.level2 == b.PerimeterID && b.PerimeterLevelID == 2) ||
      (a.level3 == b.PerimeterID && b.PerimeterLevelID == 3)

它生成这个sql查询：

select * from  A a
join B b on (a.level1= b.PerimeterID and  b.PerimeterLevelID = 1)
where (a.level2= b.PerimeterID and  b.PerimeterLevelID = 2)
       OR (a.level3= b.PerimeterID and  b.PerimeterLevelID = 3))

我也尝试过林克尔，但它不能将OR转换成linq

不能将SQL转换为LINQ:或

转换这个sql查询所必须做的事情

Answer 1

内部连接等效于筛选的交叉连接。那你觉得呢

from a in A
from b in B 
where (a.level1 == b.PerimeterID && b.PerimeterLevelID == 1) ||
      (a.level2 == b.PerimeterID && b.PerimeterLevelID == 2) ||
      (a.level3 == b.PerimeterID && b.PerimeterLevelID == 3)
select new {a,b};

Answer 2

我认为这个查询会有帮助。

var query = from a in context.A
            join b1 in context.B
                on new { Perimeter = a.level1, LevelID = 1 }
                equals new { Perimeter = b1.PerimeterID, LevelID = b1.PerimeterLevelID }
            join b2 in context.B
                on new { Perimeter = a.level2, LevelID = 2 }
                equals new { Perimeter = b2.PerimeterID, LevelID = b2.PerimeterLevelID }
            join b3 in context.B
                on new { Perimeter = a.level3, LevelID = 3 }
                equals new { Perimeter = b3.PerimeterID, LevelID = b3.PerimeterLevelID }
            select new
            {
                a,
                b1,
                b2,
                b3
            };

Answer 3

你可以试试DefaultIfEmpty()。联接的行为与此命令类似于左联接。

from a in A
from b in B.DefaultIfempty()
where (   (a.level1== b.PerimeterID &&  b.PerimeterLevelID == 1)
       || (a.level2== b.PerimeterID &&  b.PerimeterLevelID == 2)
       || (a.level3== b.PerimeterID &&  b.PerimeterLevelID == 3))