LINQ＆amp; SQL查询帮助：在两列上做一个截然不同的？

Question

如何根据SELECT AND DISTINCT得到FromLinkID结果ToLinkID？

如果我的List有以下数据，我怎样才能在LINQ中获得我的目标？

Answer 1

SELECT  DISTINCT FromLinkId, ToLinkId
FROM    mytable

要为(FromLinkId, ToLinkId)选择一条记录（最少id），假设为SQL Server：

SELECT  *
FROM    (
        SELECT  *, ROW_NUMBER() OVER (PARTITION BY FromLinkId, ToLinkId ORDER BY id) AS rn
        FROM    mytable
        ) q
WHERE   rn = 1

Answer 2

试试这个：

Select Distinct FromLinkId LinkId From MyTable 
Union 
Select Distinct ToLinkId LinkId From MyTable 

Answer 3

SELECT Name, FromLinkId, ToLinkId FROM MyTable GROUP BY FromLinkId, ToLinkId -- if there are more than one record with the same (FromLinkId, ToLinkId) pair, only one of them is displayed.

Answer 4

您可以执行以下操作：

SELECT MAX(ID), MAX(Name), FromLinkID, ToLinkID FROM MyTable 
GROUP BY FromLinkID, ToLinkID

甚至：

SELECT t.* FROM
(SELECT MAX(ID) as MaxID, FromLinkID, ToLinkID FROM MyTable  
GROUP BY FromLinkID, ToLinkID) d 
LEFT JOIN MyTable t ON d.MaxID=t.ID

Answer 5

LINQ解决方案：

List<MyObj> distinctResults = allResults
  .GroupBy(p => new {p.FromLinkID, p.ToLinkID} )
  .Select(g => g.First())
  .ToList();

希望它对某人有所帮助。

Helpful related SO question.

Answer 6

列出distinctResults = allResults   。选择（p =＆gt; new {p.FromLinkID，p.ToLinkID}）   。不同（）   .ToList（）;