Question

我需要将Linq中的以下相关子查询转换为Sql。我能够实现左外连接部分。但是，在子查询中进行分组是我得到错误结果的地方。

SELECT 
  ae.Id,ae.Title
,(select COUNT(*) from [dbo].[AssociationEventRSVP]  where RSVPStatus='Y'
 group by  AssociationEventId, RSVPStatus having RSVPStatus='Y'
 and AssociationEventId=ar.AssociationEventId) as CountYes
,(select COUNT(*) from [dbo].[AssociationEventRSVP]  
 group by  AssociationEventId, RSVPStatus having RSVPStatus='N'
 and AssociationEventId=ar.AssociationEventId) as CountNo 
  FROM [dbo].[AssociationEvents] as ae
  left outer join AssociationEventRSVP as ar
  on ae.Id=ar.AssociationEventId

提前感谢您的帮助。

Tushar M。

Answer 1

我首先将您的查询重构为：

SELECT 
ae.Id,
ae.Title,
(select COUNT(*) FROM [dbo].[AssociationEventRSVP] WHERE RSVPStatus='Y' AND AssociationEventId=ae.Id) AS CountYes,
(select COUNT(*) FROM [dbo].[AssociationEventRSVP] WHERE RSVPStatus='N' AND AssociationEventId=ae.Id) AS CountNo 
FROM [dbo].[AssociationEvents] as ae

这是一个简单的（不一定高效的）LINQ to SQL转换：

var results = from ae in context.AssociationEvents
              select new
              {
                  ae.Id,
                  ae.Title,
                  CountYes = context.AssociationEventRSVP.Where(aer => aer.RSVPStatus == "Y" && aer.AssociationEventId == ae.Id).Count(),
                  CountNo  = context.AssociationEventRSVP.Where(aer => aer.RSVPStatus == "N" && aer.AssociationEventId == ae.Id).Count()
              };

Linq外连接在子查询中进行分组

1 个答案: