I want to convert this sql query to linq
SELECT Students.StdId, Mark.Value
FROM Departments INNER JOIN
Mark ON Departments.DepId = Mark.DepId INNER JOIN
Students ON Departments.DepId = Students.DepId AND Mark.StdId = Students.StdId
I did this, but it's wont working
from s in Students
join d in Departments on s.DepId equals d.DepId
join m in Marks on new {s.StdId, d.DepId} equals new {m.StdId, m.DepId}
select new{
SId=s.StdId,
Value=m.Value
}
Lets try with
from s in Students
join d in Departments on s.DepId equals d.DepId
join m in Marks
on new {StdId = s.StdId, DepId = d.DepId} equals new {StdId = m.StdId, DepId= m.DepId}
select new{
SId=s.StdId,
Value=m.Value
}
How about
from s in Students
join m in Marks on s.StdId equals m.StdId
join d in Departments on m.DepId equals d.DepId
select new { s.StdId, m.Value };
Related
In SQL, I would commonly inner join two or more tables to create a set and then left join to that set:
select *
from TableA
left outer join
TableB
inner join TableC on TableB.Id = TableC.TableBId
on TableA.Id = TableB.TableAId
What is the Linq equivalent of this? I'm using EF Code First.
Like this:
var result = from a in TableA
join b in TableB on a.Id equals b.TableAId into ab
from b in ab.DefaultIfEmpty()
join c in TableC on b.Id equals c.TableBId
select a;
I was able to achieve this by breaking it into two statements. First, make your inner join set, then left join to that set.
var bc = from b in TableB
join c in TableC on b.Id equals c.TableBId
select new { B = b, C = c };
var result = from a in TableA
from bcRow in bc.Where(row => a.Id equals row.B.TableAId).DefaultIfEmpty()
select new { A = a, B = bcRow.B, C = bcRow.C };
Hi All my following query returns results like this:
lstView.DataSource = (from h in context.HolidayMains
join hd in context.HolidayDetails on h.Id equals hd.HolidayMainId into hd2
from hd in hd2.DefaultIfEmpty()
join e in context.Employees on h.CreatedBy equals e.Id into e2
from e in e2.DefaultIfEmpty()
join o in context.OfficeLocations on hd.OfficeLocation equals o.Id into o2
from o in o2.DefaultIfEmpty()
select new
{
h.HolidayTitle,
h.Date,
OfficeLocation = o.Name,
CreatedBy = e.Name,
h.Id
}).ToList();
But I need result like this :
How it can be done?
I am trying to outer join multiple tables. Here I have pasted my code what I am trying to do.
from o in entities.O
join p in entities.P on o.PID equals p.ID
join dC in entities.C on o.DCID equals dC.ID
join hC in entities.C on o.HCID equals hC.ID
join e in entities.E on pat.AN equals e.UID
join oT in entities.OT on o.OT equals oT.ID
join plt in entities.PLT on p.LT equals plt.ID
join puO in entities.PUO on o.PUTId equals puO.ID into pots
from x in pots.DefaultIfEmpty()
join op in entities.OP on o.OPID equals op.ID
join prt in entities.PatientRelationshipTypes on pat.PRTId equals prt.ID
join secPRT in entities.PRT on pat.SRTId equals secPRT.ID
join patDiagCode in entities.PDiagnosisCodes on pat.ID equals patDiagCode.PID
//from y in pdc.DefaultIfEmpty()
join diagCode in entities.DCodes on patDiagCode.CodeID equals diagCode.ID into dc
from z in dc.DefaultIfEmpty()
where o.ID == orderId
//from x in pots.DefaultIfEmpty()
//from y in pdc.DefaultIfEmpty()
...
...
How do I write correct syntax for multiple outer join in Linq?
Thanks in advance
I want to convert this code to linq:
select t1.title, COUNT(*)as num
from t1 INNER join t2 on t2.gId = t1.Id
group by t1.title, t1.cId
having t1.cId = 2
I tried this below code:
from p in db.t1s join r in db.t2s on p.Id equals r.gId
where p.cId == 2
group p by p.title into g
select new{ name = from o in g select o.title, num = g.Count()}
But this doesn't return COUNT correctly.
please guide me how can I solve the problem
thanks
Without sample data its hard to get it right, but try this snippet
from p in db.t1s
join r in db.t2s on p.Id equals r.gId
where p.cId == 2
group p by new {p.title, p.cId} into grouped
select new{ name = grouped.Key.title, num = grouped.Count()}
Also, note that this sql:
select t1.title, COUNT(*)as num
from t1 INNER join t2 on t2.gId = t1.Id
group by t1.title, t1.cId
having t1.cId = 2
Will always return 1 as result of COUNT(*). The reason is that you have filtering t1.cId = 2 and grouping by t1.cId as second parameter.
I have 3 tables which named Player, PlayerDetails and Team. I want to write a linq statement such as
from p in Player join d in PlayerDetails on p.ID equals d.PID
and then right join team table, Player has a column named TID which face to Team table's ID.
I have tried to write a statement like
from p in Player join d in PlayerDetails on p.ID equals d.PID into PlayerGroup
from t in team join g in PlayerGroup on t.ID equals g.p.ID
It certainly can't work. I'm not sure how to write such type of query statement, table left join table2 then right join table3.
Who can help?
I believe you could do something like this:
var LeftJoin =
from p in Player
join d in PlayerDetails on p.ID equals d.PID into pd
from d in pd.DefaultIfEmpty()
select new
{
pID = p.ID,
pTID = p.TID,
dID = d.ID
};
var RightJoin =
from t in Team
join l in LeftJoin on t.ID equals l.pTID into tl
from l in tl.DefaultIfEmpty()
select new
{
tID = t.ID,
pID = l.pID,
pTID = l.PTID,
dID = l.dID
};
To do everything in one query, I think you could do (not tested) something like this:
var RightJoin =
from t in Team
join l in
(from p in Player
join d in PlayerDetails on p.ID equals d.PID into pd
from d in pd.DefaultIfEmpty()
select new
{
pID = p.ID,
pTID = p.TID,
dID = d.ID
})
on t.ID equals l.pTID into tl
from l in tl.DefaultIfEmpty()
select new
{
tID = t.ID,
pID = l.pID,
pTID = l.PTID,
dID = l.dID
};