c# - 将 Linq to Sql 查询转换为更好的 sql

Question

所以我需要一些带有 sql 查询的东西。从 linq 生成的 sql 看起来很差，存储过程超时。

这就是我想要做的。

两个表，如下所示:

dbo.Links
-------------
Id
Url
Title

还有一个看起来像这样

dbo.Link_Counts
-----------------
Url
Count

我想做的是编写一个执行此操作的 sql 查询

var linkCounts = Links.GroupBy(x => x.Url)
                 .Select(grp => new Link_Counts 
                  {
                      Url = grp.First().Url,
                      Count = grp.Count()
                  });

InsertAllOnSubmit(linkCounts);
SubmitChanges();

我尝试使用的部分是由此生成的 sql 是

    INSERT INTO Link_Counts (Url, Count)
SELECT (
    SELECT [t3].[URL]
    FROM (
        SELECT TOP (1) [t2].[URL]
        FROM [Links] AS [t2]
        WHERE (([t1].[URL] IS NULL) AND ([t2].[URL] IS NULL)) OR (([t1].[URL] IS NOT NULL) AND ([t2].[URL] IS NOT NULL) AND ([t1].[URL] = [t2].[URL]))
        ) AS [t3]
    ) AS [Url], [t1].[value] AS [Count]
FROM (
    SELECT COUNT(*) AS [value], [t0].[URL]
    FROM [Links] AS [t0]
    GROUP BY [t0].[URL]
    ) AS [t1]
END

存储过程显然运行时间过长。

任何帮助都将不胜感激。

谢谢

Answer 1

如果你想手写SQL:

insert into link_counts (url, count)
select url, count(0)
from links
group by url

或者，如果您只想修复 LINQ 查询以生成更好的 SQL:

var linkCounts = 
    Links.GroupBy(x => x.Url)
         .Select(g => new Link_Counts
             {
                 Url = g.Key,
                 Count = g.Count()
             };