Question

如何使用内部联接，左外部联接，分组依据和两个计数的查询转换为linq？

SELECT
    c.EndowmentID,
    COUNT(DISTINCT f.CriterionID) AS RequiredCriteria,
    COUNT(r.ChoiceID) AS Response
FROM
    Criteria c
INNER JOIN
    Filters f
ON
    c.ID = f.CriterionID
LEFT OUTER JOIN 
    Responses r
ON
    f.ChoiceID = r.ChoiceID
WHERE
    f.IsRequirement = 1
GROUP BY
    c.EndowmentID;

这是我到目前为止所做的：

            var result =
                from c in context.Criteria
                join f in context.Filters on c.ID equals f.CriterionID
                join r in context.Responses on f.ChoiceID equals r.ChoiceID into resfil
                from rf in resfil.DefaultIfEmpty()
                group rf by c.EndowmentID into grouped
                select new 
                {
                    EndowmentID = grouped.Key,
                    Requirements = grouped.Count(t=>t.CriterionID),
                    Response = grouped.Count(t=>t.ChoiceID)
                };

Answer 1

您需要group使用匿名类。这样您就可以访问select声明

中的所有表格

group new { c, f, rf } by c.EndowmentID into grouped

SQL：COUNT(DISTINCT f.CriterionID) AS RequiredCriteria,

首先选择f.CriterionID列，Distinct()，Count()

即可编写

RequiredCriteria = grouped.Select(x => x.f.CriterionID).Distinct().Count()

SQL：COUNT(r.ChoiceID)

Response = grouped.Select(x => x.rf.ChoiceID).Count()

左外连接和多个计数SQL到LINQ

1 个答案: