在Linq To SQL C#.NET 3.5中保留左外连接和存在
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03-07-2019 - |
题
我坚持从LINQToSQL转换左外连接,返回唯一的父行。
我有2个表(Project,Project_Notes,它是由Project_ID链接的1-many关系)。我在2表上的多个列上进行关键字搜索,如果Project_Notes中的列包含关键字,我只想返回唯一项目。我有这个linqtoSQl序列,但它似乎返回多个Project行。也许在LINQ中以某种方式做一个Exist
?或者也许是某种类型的群体?
这是LINQToSQL:
query = from p in query
join n in notes on p.PROJECT_ID equals n.PROJECT_ID into projectnotes
from n in notes.DefaultIfEmpty()
where n.NOTES.Contains(cwForm.search1Form)
select p;
这是从profiler
生成的SQLexec sp_executesql N'SELECT [t2]。[Title],[t2]。[State],[t2]。[PROJECT_ID], [t2]。[PROVIDER_ID],[t2]。[CATEGORY_ID],[t2]。[城市],[t2]。[UploadedDate], [t2]。[SubmittedDate],[t2]。[Project_Type] FROM(SELECT ROW_NUMBER()OVER(ORDER BY [t0]。[UploadedDate])AS [ROW_NUMBER],[t0]。[Title],[t0]。[State],[t0]。[PROJECT_ID], [t0]。[PROVIDER_ID],[t0]。[CATEGORY_ID],[t0]。[城市],[t0]。[UploadedDate], [t0]。[SubmittedDate],[t0]。[Project_Type] FROM [dbo]。[PROJECTS] AS [t0] LEFT OUTER JOIN [dbo]。[PROJECT_NOTES] AS [t1] ON 1 = 1 WHERE([t1]。[NOTES] LIKE @ p0)AND ([t0] .SubmittedDate] <!> gt; = @ p1)AND([t0]。[SubmittedDate] <!> lt; @ p2)AND([t0]。[PROVIDER_ID] = @ p3)AND([t0]。[CATEGORY_ID]为空))AS [t2] WHERE [t2]。[ROW_NUMBER] BETWEEN @ p4 + 1 AND @ p4 + @ p5 ORDER BY [t2]。[ROW_NUMBER]',N'@ p0 varchar(9),@ p1 datetime,@ p2 datetime,@ p3 int,@ p4 int,@ p5 int',@ p0 ='%chicago%',@ p1 =''2000-09-02 00:00:00:000'',@ p2 =''2009-03-02 00:00:00:000 '',@ P3 = 1000,@ P4 = 373620,@ P5 = 20
此查询返回结果中1-many关系的所有多个部分。我在这里找到了如何在LINQ中执行Exists
。 http:/ /www.linq-to-sql.com/linq-to-sql/t-sql-to-linq-upgrade/linq-exists/
这是使用databind()
的LINQToSQL:
query = from p in query
where (from n in notes
where n.NOTES.Contains(cwForm.search1Form)
select n.PROJECT_ID).Contains(p.PROJECT_ID)
select p;
生成的SQL语句:
exec sp_executesql N'SELECT COUNT(*)AS [value] FROM [dbo]。[PROJECTS] AS [t0] WHERE (EXISTS(从[dbo]中选择NULL [EMPTY]。[PROJECT_NOTES] AS [t1] WHERE ([t1] .PROJECT_ID] =([t0]。[PROJECT_ID]))AND([t1]。[NOTES] LIKE @ p0)))AND ([t0]。[SubmittedDate] <!> gt; = @ p1)AND([t0]。[SubmittedDate] <!> lt; @ p2)AND([t0]。[PROVIDER_ID] = @ p3)AND([t0]。[CATEGORY_ID] IS NULL)',N'@ p0 varchar(9),@ p1 datetime,@ p2 datetime,@ p3 int',@ p0 ='%chicago%',@ p1 =''2000-09-02 00:00:00:000'',@ p2 =''2009-03-02 00:00:00:000 '',@ P3 = 1000
我使用<=>从<=>获得SQL超时。
解决方案
它似乎正在返回多个项目行
是的,这就是加入的方式。如果一个项目有5个匹配的笔记,它会显示5次。
如果问题是什么 - <!>“加入<!>”;是错误的成语!
您希望将项目过滤到其注释包含特定文本的项目:
var query = db.Project
.Where(p => p.Notes.Any(n => n.NoteField.Contains(searchString)));
其他提示
您将不得不使用DefaultIfEmpty扩展方法。关于SO的一些问题已经显示出如何做到这一点。这是一个很好的例子: