I have a query like that and it works normally. If a student gets more than one course, it list all of them:
SELECT ks.KullaniciKodu as username, ks.Sifre as password, k.adi as firstname, k.soyadi as lastname, k.Email as email,
MAX(CASE WHEN c.DERSKODU = 'ENF100' THEN 'ENF100' ELSE '' END)As course1,
MAX(CASE WHEN c.DERSKODU = 'ATA101' THEN 'ATA101' ELSE '' END) As course2,
MAX(CASE WHEN c.DERSKODU = 'TDB101' THEN 'TDB101' ELSE '' END) As course3,
MAX(CASE WHEN c.DERSKODU = 'İNG101' THEN 'İNG101' ELSE '' END) As course4
FROM Kayit k
JOIN DersNotu dn ON dn.KayitNo = k.KayitNo
JOIN Ders c ON c.DersKayitNo = dn.DersKayitNo AND c.DERSKODU IN ('ENF100','ATA101','TDB101', 'İNG101') AND c.DONEM = '201512'
JOIN KullaniciSifre ks ON ks.KullaniciKodu = k.KullaniciKodu
GROUP BY ks.KullaniciKodu, ks.Sifre, k.adi, k.soyadi, k.Email
But when i convert it to Linq (to Entity), it only gets one course or all courses are null. Where is the difference and problem in this code?
from k in db.Kayit
join dn in db.DersNotu on k.KayitNo equals dn.KayitNo
join c in db.Ders on dn.DersKayitNo equals c.DersKayitNo
join ks in db.KullaniciSifre on k.KullaniciKodu equals ks.KullaniciKodu
where
(new string[] { "ENF100", "ATA101", "TDB101", "İNG101" }).Contains(c.DersKodu) &&
c.Donem == 201512
group new { ks, k, c } by new
{
ks.KullaniciKodu,
ks.Sifre,
k.Adi,
k.Soyadi,
k.Email
} into g
select new
{
KullaniciKodu = g.Key.KullaniciKodu,
Sifre = g.Key.Sifre,
Adi = g.Key.Adi,
Soyadi = g.Key.Soyadi,
Email = g.Max(p => (
p.k.Email == string.Empty ? "NULL" : p.k.Email)),
Course1 = g.Max(p => (
p.c.DersKodu == "ENF100" ? "ENF100,1" : "NULL,1")),
Course2 = g.Max(p => (
p.c.DersKodu == "ATA101" ? "ATA101,1" : "NULL,1")),
Course3 = g.Max(p => (
p.c.DersKodu == "TDB101" ? "TDB101,1" : "NULL,1")),
Course4 = g.Max(p => (
p.c.DersKodu == "İNG101" ? "İNG101,1" : "NULL,1"))
}
Using MAX in SQL is just a trick to work-around the problem. You should not convert that explicitly to LINQToEntity. The problem here is you use Max against strings. In your case the NULL,1 seems be always selected as max except for the TDB101,1.
The actual logic here is such as for ENF100, if any one found, project for "ENF100", otherwise project for "NULL,1". The same logic for others. So it should be like this:
Course1 = g.Any(p => p.c.DersKodu == "ENF100") ? "ENF100,1" : "NULL,1",
Course2 = g.Any(p => p.c.DersKodu == "ATA101") ? "ATA101,1" : "NULL,1",
Course3 = g.Any(p => p.c.DersKodu == "TDB101") ? "TDB101,1" : "NULL,1",
Course4 = g.Any(p => p.c.DersKodu == "İNG101") ? "İNG101,1" : "NULL,1"
Also the Email is projected wrong, it is already included in the group key, so you can just project it via the group key:
Email = g.Key.Email
Related
The query below should be selecting a list of information from different tables, and should also bring back a list of VehicleNames that are related to each ID coming back from db.Reservations
The query brings back data, but the list of VehicleNames only has one record, and it should bring back anywhere up to 5 records, depending on how many vehicles were reserved for that specific instance. I have tried adding a foreach to the VehicleName line in the select but I don't think I am using it right. Does anyone have any ideas as to how I can retrieve the list of values I need?
var query = from r in db.Reservations
let e = db.Employees.Where(x => r.RequestorID == x.ColleagueID).FirstOrDefault()
let rtv = db.ReservationToVehicle.Where(x => r.ID == x.ReservationID).FirstOrDefault()
let rs = db.ReservationStatus.Where(x => r.ID == x.ReservationID).FirstOrDefault()
let rst = db.ReservationStatusTypes.Where(x => rs.ReservationStatusTypeID == x.ID).FirstOrDefault()
select new
{
StartDate = r.StartDate,
EndDate = r.EndDate,
Destination = r.Destination,
PurposeOfTrip = r.PurposeOfTrip,
TransportingStudents = r.TransportStudentsFG,
EmployeeName = e.FirstName + " " + e.LastName,
ApprovalStatus = rst.StatusType,
ThemeColor = r.ThemeColor,
VehicleName = (from v in db.Vehicles
where v.ID == rtv.VehicleID
select v.VehicleName).ToList()
};
EDIT: Updated query, still uncertain how to get back list of Vehicles that have been reserved
var query = from r in db.Reservations
let e = db.Employees.Where(x => r.RequestorID == x.ColleagueID).FirstOrDefault()
let rtv = db.ReservationToVehicle.Where(x => r.ID == x.ReservationID).Select(y => y.VehicleID).ToList()
let rs = db.ReservationStatus.Where(x => r.ID == x.ReservationID).FirstOrDefault()
let rst = db.ReservationStatusTypes.Where(x => rs.ReservationStatusTypeID == x.ID).FirstOrDefault()
select new
{
StartDate = r.StartDate,
EndDate = r.EndDate,
Destination = r.Destination,
PurposeOfTrip = r.PurposeOfTrip,
TransportingStudents = r.TransportStudentsFG,
EmployeeName = e.FirstName + " " + e.LastName,
ApprovalStatus = rst.StatusType,
ThemeColor = r.ThemeColor,
VehicleName = (from v in db.Vehicles
where v.ID == rtv.VehicleID
select v.VehicleName).ToList()
};
rtv.VehicleID does not exist anymore, now rtv comes back with a list of IDs....I need to be able to get into that list to find where v.ID is IN the rtv list
Looks like people already told you this in the comments, but here's the code that ought to work:
var query = from r in db.Reservations
let e = db.Employees.Where(x => r.RequestorID == x.ColleagueID).FirstOrDefault()
let rtv = db.ReservationToVehicle.Where(x => r.ID == x.ReservationID).Select(y => y.VehicleID)
let rs = db.ReservationStatus.Where(x => r.ID == x.ReservationID).FirstOrDefault()
let rst = db.ReservationStatusTypes.Where(x => rs.ReservationStatusTypeID == x.ID).FirstOrDefault()
select new
{
StartDate = r.StartDate,
EndDate = r.EndDate,
Destination = r.Destination,
PurposeOfTrip = r.PurposeOfTrip,
TransportingStudents = r.TransportStudentsFG,
EmployeeName = e.FirstName + " " + e.LastName,
ApprovalStatus = rst.StatusType,
ThemeColor = r.ThemeColor,
VehicleName = (from v in db.Vehicles
where rtv.Contains(v.ID)
select v.VehicleName).ToList()
};
I'd also recommend looking at setting up navigation properties between your entities. Your query could be much simpler, something like this:
var query = from r in db.Reservations
let e = r.Requestor
let rs = r.ReservationStatus
let rst = rs.ReservationStatusType
select new
{
StartDate = r.StartDate,
EndDate = r.EndDate,
Destination = r.Destination,
PurposeOfTrip = r.PurposeOfTrip,
TransportingStudents = r.TransportStudentsFG,
EmployeeName = e.FirstName + " " + e.LastName,
ApprovalStatus = rst.StatusType,
ThemeColor = r.ThemeColor,
VehicleName = r.Vehicles.Select(v => v.VehicleName).ToList()
};
I’m working with MVC 5 and I’m quite new on it. How can convert the below sql code to lambda expression. Basically what I’m trying to do is to show all records that ProductID not exist in Scrap Table
Select * from Product
where ProductID not in (Select ProductID from Scrap where ref = '123')
and active = 1
I believe your query is equivalent to:
select p.*
from Product p
join Scrap s on p.ProductID = s.ProductID
where
s.ref <> '123'
and p.active = 1
If so, try this:
from p in db.Products
join s in db.Scraps on p.ProductID equals s.ProductID
where s.Ref != "123" && p.Active == 1
select p
Try
var query =
from p in db.Products
where !(from s in db.Scrap
where s.ref == '123'
select s.ProductId)
.Contains(p.ProductId)
&& p.Active = 1
Try something like:
var products = (from p in db.Products //db is an instance of my datacontext
where !db.Scrap.Any(s => s.ProductId == p.ProductId && s.ref == "123")
&& p.active == 1 // p.active == true if active is of type bit in sql
select p);
I have a List generated from Linq to Entities query. In which, I need to get a unique records based on BibId. I have tried changing the query but no help to get the unique records based on BibId.
Query
aa.NewBibContentsModel = (from x in db.BibContents
where (x.TagNo == "245" && x.NormValue == aa.CurrentTitle) || (x.TagNo == "020" && x.NormValue == aa.CurrentISBN) || (x.TagNo == "022" && x.NormValue == aa.CurrentISBN)
select new
{
BibId = x.BibId,
Title = (from a in db.BibContents where a.BibId == x.BibId && a.TagNo == "245" orderby a.Id ascending select a.NormValue),
//Tit = (from a in db.BibContents where a.BibId == line.BibId && a.TagNo == "245" && a.Sfld == "a" select a.NormValue).FirstOrDefault(),
Author = (from a in db.BibContents where a.BibId == x.BibId && splitted.Contains(a.TagNo) && a.NormValue != null select a.TagNo).FirstOrDefault(),
ISBN = (from a in db.BibContents where a.BibId == x.BibId && a.NormValue != null && (a.TagNo == "020" || a.TagNo == "022") orderby a.Id ascending select a.NormValue)
}).AsEnumerable().Select(x => new BibContentsModel
{
BibId = x.BibId,
Title = string.Join(" ", x.Title),
Author = string.Join(" ", (from a in db.BibContents where a.BibId == x.BibId && a.TagNo == x.Author orderby a.Id select a.NormValue)),
ISBN = string.Join(" ", x.ISBN)
}).ToList();
Any help to this problem will be appreciated.
Thanks
What you're trying to achieve is know as Distinct By. MoreLinq has a function for it. The syntax would look like:
(from x in db.BibContentsNo == "022")
... // your query
}).AsEnumerable()
.DistinctBy(x => x.BibId) // <= MoreLinq
What is does is group the records by BibId and take the first element of each group.
You can download MoreLinq as a NuGet package.
I am trying to replicate the following SQL query with linq. On SQL Server it takes a fraction of a second to run:
select g.reference, count(*)
from isis.dbo.[group] as g inner join
isis.dbo.enrolment as e on g.groupid = e.groupid inner join
isis.dbo.student as s on e.studentid = s.studentid inner join
isis.dbo.progression as p on s.studentid = p.studentid
where p.academicyear = '12/13' and g.istutorgroup = 1
group by reference
In my MVC application I am passing a listing of "TutorGroups" to the view. For each tutor group in the view I need to display various information about them, one item being the number of "Progression" interviews they have had.
I have tried a couple of methods but they both take upwards of 30 secs to run in my MVC application:
<%TTMrequired = tg.Enrolments
.SelectMany(e => e.Student.Progressions
.Where(p => p.TTMChecked == false &&
p.TTMInterview == true &&
p.AcademicYear == year))
.Count(); %>
and
<%TTMrequired = tg.Enrolments
.Where(e => e.Student.Progressions
.Any(p => p.TTMChecked == false &&
p.TTMInterview == true &&
p.AcademicYear == year))
.Count(); %>
Anyone got any suggestions on how I can speed this up? I suspect the problem is me trying to do it a stupid way - it usually is!
You could try doing a Sum of counts instead of a SelectMany:
tg.Enrolments.Sum(e => e.Student.Progressions
.Count(p => p.TTMChecked == false &&
p.TTMInterview == true &&
p.AcademicYear == year)
);
Should be written using this syntax:
var TTMRequired = (from g in tg.Groups
join e in tg.Enrolment on g.groupid equals e.groupid
join s in tg.Students on e.studentid equals s.studentid
join p in tg.Progressions on s.studentid = p.studentid
where p.academicyear.Equals("12/13") && g.istutorgroup.Equals(1)
group g by g.reference into grp
select new {
grpRef = grp.Key,
grpCount = grp.Count()
});
Note: if g.istutorgroup is of type BIT instead of INT, consider using .Equals(true).
I need my LINQ Query to return the Product Datatype, after being grouped. It seems to be encased into an anonymous psuedo family.
I have some properties in Product that I don't care about, just needing the p.ID and p.Name etc.
The error I'm getting at the moment with this is:
The entity or complex type 'DatabaseModel.Product' cannot be constructed in a LINQ to Entities query.
This is my Method:
public static List<Product> GetSellableSpecialOffers(DatabaseEntities db)
{
var query = from p in db.Products
where (p.Visible == true && p.Active == true)
&& p.ShowInSpecialOffers == true
group p by p.FamilyID == null ? 0 : p.FamilyID into f
select new Product {
ID = f.First().ID,
Name = f.First().Name,
Cost = f.First().Cost,
RRP = f.First().RRP
};
return query.ToList();
}
What is the problem? Is there a better way around this? SQL would always return 1 record instead of encasing the object in a secondary datatype, I don't get it.
Many thanks,
EDIT 1:
My apologies for extending the specification, but I need the returned product to be programatically generated e.g.
select new Product {
ID = f.First().ID,
Name = f.First().Name,
Cost = f.OrderBy(p => p.NowCost).FirstOrDefault(),
RRP = f.First().RRP
}
or if I could strongly type the family class:
public partial class ProductFamily
{
public Product GroupedProduct
{
get
{
return this.Products.OrderBy(p => p.NowCost).FirstOrDefault();
}
}
}
Then I would do:
var query = (from p in db.Products
where (p.Visible == true && p.Active == true)
&& p.ShowInSpecialOffers == true
group p by p.ProductFamily == null ? null : p.ProductFamily into f
select f.GroupedProduct).ToList<Product>();
But I can't get either solution to work with what I have.
You can try (boring, but not sure you have the choice)
var query = from p in db.Products
where (p.Visible == true && p.Active == true)
&& p.ShowInSpecialOffers == true
group p by p.FamilyID == null ? 0 : p.FamilyID into f
select new {
ID = f.First().ID,
Name = f.First().Name,
Cost = f.OrderBy(m => m.NowCost).First().Cost,
RRP = f.First().RRP
};
return query.ToList().Select(m =>
new Product {
ID = m.ID,
Name = m.Name,
Cost = m.Cost,
RRP = m.RRP
};
EDIT
Or as pointed by Master Skeet (not exactly the same as what you tried, but much easier)
var query = from p in db.Products
where (p.Visible == true && p.Active == true)
&& p.ShowInSpecialOffers == true
group p by p.FamilyID == null ? 0 : p.FamilyID into f
select f.OrderBy(m => m.NowCost).First();
You could simply select f.First() and return the resulting data, like this:
var query = from p in db.Products
where (p.Visible == true && p.Active == true)
&& p.ShowInSpecialOffers == true
group p by p.FamilyID == null ? 0 : p.FamilyID into f
select f.First();
Then outside the method use whatever properties you need, ignoring what you don't care about (you are handling Product objects, properties should be there even if you don't need them).
Remove the word 'Product' from
select new Product{}
'select new' itself will create an anonymous type whereas you are specifying it as a Product.