LINQ查询返回的结果比整个数据库中的结果更多

Question

我有以下LINQ查询。问题是，当tblSurveys总共只有20个时，它会返回13k的结果。我做错了什么？

from s in surveyContext.tblSurveys
from st in surveyContext.tblTypes_for_Surveys
from t in surveyContext.tblSurvey_Types
where (s.Survey_Date >= startDate && s.Survey_Date <= stopDate) && 
      (s.Unsubstantiated || 
         (st.SurveyID == s.SurveyID && st.SurveyTypeID == t.SurveyTypeID && 
         t.UnsubstantiatedAvailable && (from d in surveyContext.tblDeficiencies
                                         where d.SurveyID == s.SurveyID
                                        select d.DeficiencyID).Count() == 0))
orderby s.Survey_Date
select s;

Answer 1

我可以在那里看到交叉连接，请查看＆lt; -------

           from s in surveyContext.tblSurveys
           from st in surveyContext.tblTypes_for_Surveys
           from t in surveyContext.tblSurvey_Types
           where (s.Survey_Date >= startDate && s.Survey_Date <= stopDate) && 
                 (s.Unsubstantiated || <-------
                    (st.SurveyID == s.SurveyID && st.SurveyTypeID == t.SurveyTypeID && 
                    t.UnsubstantiatedAvailable && (from d in surveyContext.tblDeficiencies
                                                   where d.SurveyID == s.SurveyID
                                                   select d.DeficiencyID).Count() == 0))
           orderby s.Survey_Date
           select s;

您似乎需要在此处执行左连接

Answer 2

您的数据库中是否设置了外键和关系？如果是这样，您可以大大简化您的查询。我还建议在.dbml文件中重命名表，这样它们就不会以'tbl'为前缀。

如果您确实设置了关系，那么您的查询可能看起来像这样：

from s in surveyContext.tblSurveys
where (s.Survey_Date >= startDate && s.Survey_Date <= stopDate) && 
     (s.Unsubstantiated || 
        (s.tblTypes_for_Surveys.Any(st => st.tblSurvey_Type.UnsubstantiatedAvailable) && s.tblDeficiencies.Count() == 0))
orderby s.Survey_Date
select s;