sql - Linq 自连接组合键

Question

请有人帮我解决这个问题。

我有一个需要连接到自身的表。该表包含一个组合键。到目前为止，以下 SQL 语句运行良好。

select * from releases as a inner join
(
select * from releases as r1
where id=50
) as x 
on (a.ParentSeriesId = x.SeriesId and a.ParentPeriod = x.Period) OR a.id=50

问题是如何将其转换为 linq。

到目前为止我得出的结果是

from a in Releases
join x in (
         (from r1 in Releases
         where
         r1.Id == 50
         select new {
         r1
         }))
         on new { a.ParentSeriesId, a.ParentPeriod, a.Id }
  equals new { ParentSeriesId = x.r1.SeriesId, ParentPeriod = x.r1.Period, Id = 50 }
select new{

}

但这会产生以下 SQL 语句

SELECT NULL AS [EMPTY]
FROM [Releases] AS [t0]
INNER JOIN [Releases] AS [t1] ON ([t0].[ParentSeriesId] = [t1].[SeriesId]) AND ([t0].[ParentPeriod] = [t1].[Period]) AND ([t0].[Id] = @p0)
WHERE [t1].[Id] = @p1

问题是我怎样才能使它成为我原来的 SQL 语句。谢谢!!

Answer 1

Linq 只支持等值连接，因为你有一个 OR 尝试下面的两个 'from' 子句

var xQuery = from r in Releases
             where r.Id == 50
             select r;

var query = from r in Releases
            from x in xQuery
            where (r.ParentSeriesId == x.SeriesId && r.ParentPeriod == x.Period) ||
                   r.Id == 50  //r.Id == x.Id
            select new
            {

            }