在Linq中加入子查询结果 [英] Join Subquery result in Linq

问题描述

我对我的另一个疑问是: 有没有一种方法可以使用一个查询的结果，然后像在SQL中一样将其进一步联接:

I am posting one more doubt of mine: Is there a way by which we can use the result of one query and then join the same further just like we do in SQL:

SELECT Applications.* , ApplicationFees.ApplicationNo, ApplicationFees.AccountFundDate1,ApplicationFees.AccountFundDate2 ,ApplicationFees.AccountFundDate3 , ApplicationFees.AccountCloseDate1, ApplicationFees.AccountCloseDate2,ApplicationFees.AccountCloseDate3,
isnull(SUBQRY11.AMNT ,0) as SCMSFEE1R,
isnull(SUBQRY12.AMNT,0) as SCMSFEE2R,
Left Join 
(
SELECT ApplicationNo,COUNT(ApplicationNo) AS CNT, SUM(Amount) as AMNT 
FROM Payments where (FEETYPE=1 AND FeePosition=1)  and (FeeDate>='2011-01-01')
and (FeeDate<='2012-01-01')
GROUP BY ApplicationNo
)SUBQRY11
ON ApplicationFees.ApplicationNo= SUBQRY11.ApplicationNo 
Left Join 
(
SELECT ApplicationNo,COUNT(ApplicationNo) AS CNT2, SUM(Amount) as AMNT 

FROM Payments where (FEETYPE=1 AND FeePosition=2) and (FeeDate>='2011-01-01') 
 and (FeeDate<='2012-01-01')
GROUP BY ApplicationNo )SUBQRY12 ON ApplicationFees.ApplicationNo=SUBQRY12.ApplicationNo

我想避免在foreach查询中使用相同的方法，因为这将非常耗时.

I want to avoid the same in foreach of the query as that will be quite time consuming.

推荐答案

是的，您可以加入子查询.像这样:

Yes, you can join sub queries. Like this:

var query = from f in db.ApplicationFees
            join sub in (from p in db.Payments
                         where p.Type == 1 && p.Position == 1 && 
                               p.Date >= fromDate && p.Date <= toDate
                         group p by p.ApplicationNo into g
                         select new {
                              ApplicationNo = g.Key,
                              CNT = g.Count(),
                              AMNT = g.Sum(x => x.Amount)
                         }) 
           on f.ApplicationNo equals sub.ApplicationNo into feePayments
           select new { Fee = f, Payments = feePayments };

但是在单个查询中编写它不是很容易维护.考虑分别从定义子查询组成查询:

But writing it in single query is not very maintainable. Consider to compose your query from sub-queries defined separately:

var payments = from p in db.Payments
               where p.Type == 1 && p.Position == 1 && 
               p.Date >= fromDate && p.Date <= toDate
               group p by p.ApplicationNo into g
               select new {
                    ApplicationNo = g.Key,
                    CNT = g.Count(),
                    AMNT = g.Sum(x => x.Amount)
              };

var query = from f in db.ApplicationFees
            join p in payments 
               on f.ApplicationNo equals p.ApplicationNo into feePayments
            select new { Fee = f, Payments = feePayments };

这篇关于在Linq中加入子查询结果的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！