Linq SQL with Select MAX Sub Query

Question

我有以下SQL查询，其中有一个子查询，因此只有最大值在结果集中:

Select 
t.ID,
r.ResultIdentifier,
p.ProductID,
r.Status,
r.Start
from Result r , Transact t, Product p
WHERE r.ResultIdentifier =  (Select MAX(r2.ResultIdentifier) from Result r2 
where r2.Status = 'Fail'
and r2.ID = r.ID
and r2.Start >= getdate() - 30)
and r.ID = t.ID
and p.productID = 9
and t.productID = p.productID

我正在尝试将此转换为LINQ查询

var failures = from result in db.Results
join transact in db.Transacts on result.ID equals transact.ID
join product in db.Products on transact.ProductID equals product.ProductID
where result.ResultIdentifier == ??
.....
select new{ ID = transact.ID,
...etc

我真的很纠结于LINQ中的最大ResultIdentifier -尝试了。max()的多种变化，但似乎无法得到正确的结果。欢迎提出任何建议。

Answer 1

您可以使用max关键字，抱歉使用方法语法，因为我可以看到您正在使用查询:(

应该像下面这样

where result.ResultIdentifier == (Results.Max().Where(x => x.Status.equals("Fail") && x.id == result.id && x.start => Datetime.Now().Add(-30)).Select(x => x.ResultIdentifier))

Answer 2

尝试以下查询:

var results = db.Results;
var failedResults = results
.Where(r => r.Status == "Fail" && r.Start >= DataTime.Date.AddDays(-30));
var failures = 
from result in results
join transact in db.Transacts on result.ID equals transact.ID
join product in db.Products on transact.ProductID equals product.ProductID
from failed in failedResults
.Where(failed => failed.ID == result.ID)
.OrderByDescending(failed => failed.ResultIdentifier)
.Take(1)
where result.ResultIdentifier == failed.ResultIdentifier
.....
select new{ ID = transact.ID,
...etc