I have a query which is connecting two tables that is header and detail table and in the having clause i have to check whether total mark of the header should equal to the sum of the detail marks.
Query is :-
select h.ExamID,h.ExamID,max(h.TotalMark) as TotalMark
from ExamMasters h
join ExamDetails d on h.ExamID=d.ExamID
group by h.ExamID,h.ExamName
having max(h.TotalMark)=sum(d.Mark)
I just want to convert this query to linq syntax.
Can anybody help please.
Regards,
Ajith
It should be:
var res = from h in ExamMasters
join d in ExamDetails on h.ExamID equals d.ExamID
group new { h, d } by new { h.ExamID, h.ExamName } into hdg
let max = hdg.Max(x => x.h.TotalMark)
where hdg.Sum(x => x.d.Mark) == max
select new
{
hdg.Key.ExamID, hdg.Key.ExamName, TotalMark = max
};
Note the use of group ... by ... into and the fact that to have both h and d after the group by I had to put them in a new { h, d }.
Related
I'm trying to convert my SQL statement to a Linq statement and I'm not sure how to add the second COUNT to it. This is my SQL statement
SELECT l.Campus_Name, Labs = COUNT(*), LabsWithSubnets = COUNT(s.Lab_Space_Id)
FROM vw_Lab_Space l
LEFT JOIN vw_Subnet s on l.Lab_Space_Id = s.Lab_Space_Id
GROUP BY l.Campus_Name
ORDER BY 1
and this is my LINQ statement so far:
from l in Vw_Lab_Space
from s in Vw_Subnet
.Where(s => s.Lab_Space_Id == l.Lab_Space_Id)
.DefaultIfEmpty() // <=- triggers the LEFT JOIN
group l by new { l.Campus_Name } into g
orderby g.Key.Campus_Name
select new {
Campus_Name = g.Key.Campus_Name,
Labs = g.Count()
}
So I have everything but the LabsWithSubnets part in there. I'm just not sure how to add that in as I can't just do an s.Lab_Space_id.Count() in the select statement.
If you need table structure and sample data please see Need help creating an OUTER JOIN to count spaces.
Using your query as a basis, you need the groups to include s so you can count when non-null (I also removed the unnecessary anonymous object around the grouping key):
from l in Vw_Lab_Space
from s in Vw_Subnet
.Where(s => s.Lab_Space_Id == l.Lab_Space_Id)
.DefaultIfEmpty() // <=- triggers the LEFT JOIN
group new { l, s } by l.Campus_Name into g
orderby g.Key
select new {
Campus_Name = g.Key,
Labs = g.Count(),
LabsWithSubnets = g.Count(ls => ls.s != null)
}
However, rather than translate the SQL, I would probably take advantage of LINQ's group join to handle the query slightly differently:
var ans = from l in Vw_Lab_Space
join s in Vw_Subnet on l.Lab_Space_Id equals s.Lab_Space_Id into sj
group new { l, sj } by ls.Campus_Name into lsjg
select new {
Campus_Name = lsjg.Key,
NumLabs = lsjg.Count(),
LabsWithSubnets = lsjg.Sum(lsj => lsj.sj.Count())
};
PS Even in your query, I would use join...from...DefaultIfEmpty rather than from...from...where but depending on your database engine, may not matter.
I'm having trouble getting my Linq statemnt to work when doing an outer join and a group by. Here's a SQL version of what I'm trying to accomplish:
select p.PRIMARY_KEY, min(p.EFFECTIVE_DATE), sum(IsNull(c.PAID_INDEMNITY, 0))
from PRMPOLCY p
left outer join CLMMAST c on p.PRIMARY_KEY = c.POLICY_NO
where p.UNDERWRITER_UID = 93
GROUP BY p.PRIMARY_KEY
Here's what I have in Linq (which doesn't work):
var result = from p in context.PRMPOLCies
join c in context.CLMMASTs on p.PRIMARY_KEY equals c.POLICY_NO into polClm
where (p.UNDERWRITER_UID == underwriter)
from grp in polClm.DefaultIfEmpty()
group grp by p.PRIMARY_KEY into g
select new PolicySummation()
{
PolicyNo = g.Key,
Incurred = g.Sum(grp => grp.PAID_INDEMNITY ),
EffDate = g.Min(grp => grp.PRMPOLCY.EFFECTIVE_DATE
};
Beating my head against the wall trying to figurwe this out!
Assuming you have a navigation property set up between PRMPOLCY and CLMMAST, you shouldn't need to specify the join explicitly. It's much easier to express most queries in linq without explicit joins, but rather treating your structures as a hierarchy. I don't know the specifics of your model property names, but I'd take a guess that something like this would work.
var result =
from p in context.PRMPOLCies
where (p.UNDERWRITER_UID == underwriter)
select new PolicySummation {
PolicyNo = p.PRIMARY_KEY,
Incurred = p.CLMASTs.Select(c => c.PAID_INDEMNITY).DefaultIfEmpty().Sum(),
EffDate = p.EFFECTIVE_DATE,
};
You need to include both your tables in the group clause like this:
group new { p, grp } by p.PRIMARY_KEY into g
Then in your Sum / Min
g.Sum(grp => grp.grp == null ? 0 : grp.grp.PAID_INDEMNITY )
g.Min(grp => grp.p.PRMPOLCY.EFFECTIVE_DATE)
I am trying to get from 3 related tables by using LINQ. But when I use 2 joins, the result takes only elements getting from 2nd join. Here is my code:
var myAssList = mldb.Assigns
.Join(mldb.Lists,
a => a.list_id,
l => l.id,
(a, l) => new {
Assign = a,
List = l
})
.Where(a => a.Assign.assigned_to == "myname")
.Join(mldb.Elements,
li => li.List.id,
e => e.parent_server_id,
(li, e) => new {
Element = e
});
var jsonSerialiser = new JavaScriptSerializer();
var listListJson = jsonSerialiser.Serialize(myAssList);
this Json return only attributes from Element(e) and List(li). But I want to get also the attributes from Assign(a).
The SQL query I am trying to realize in LINQ is that:
select * from Assigns
inner join Lists
on Assigns.server_list_id=Lists.id
inner join Elements
on Lists.id=Elements.parent_id
where Assigns.assigned_to='myname'
So, how can I get the attributes from the first join also (from "a", "l" and "e")?
You can access Assign entity from outer sequence li variable:
.Join(mldb.Elements,
li => li.List.id,
e => e.parent_server_id,
(li, e) => new {
Element = e,
Assign = li.Assign // here
});
from a in mldb.Assigns
join l in mldb.Lists on a.list_id equals l.id
join e in mldb.Elements on l.id equals e.parent_server_id
where a => a.Assign.assigned_to == "myname"
select new { Assign = a, Element = e }
This is so called "query syntax". It makes LINQ expressions looks like SQL queries.
In the end they are translated to IEnumerable extension methods. If you want
to join multiple tables then query syntax is more readable. Another useful feature
of query syntax is let clause. With the aid of it, you can declare additional variables
inside your queries.
how to use group by in Linq.
SqlServer Sample
select
ActionGroupName,
sum(cast(isnull(solicit_count,0) as int)) as 'SolicitCount'
from
[solicits]
group by
ActionGroupName
my linq version
var groupbyfilter = from v in lstSale
group v by v.ActionGroupName into g
select g.ActionGroupName, sum(g.solicit_count)
i am not getting it in proper way.
Try:
var groupbyfilter = from v in lstSale
group v by v.ActionGroupName into g
select new
{
ActionGroupName = g.Key,
Sum = g.Sum(x => x.solicit_count)
};
I am trying to figure out how to go about writing a linq query to perform an aggregate like the sql query below:
select d.ID, d.FIRST_NAME, d.LAST_NAME, count(s.id) as design_count
from tbldesigner d inner join
TBLDESIGN s on d.ID = s.DESIGNER_ID
where s.COMPLETED = 1 and d.ACTIVE = 1
group by d.ID, d.FIRST_NAME, d.LAST_NAME
Having COUNT(s.id) > 0
If this is even possible with a linq query could somebody please provide me with an example.
Thanks in Advance,
Billy
A more direct translation of your original SQL query would look like this:
var q =
// Join tables TblDesign with TblDesigner and filter them
from d in db.TblDesigner
join s in db.TblDesign on d.ID equals s.DesignerID
where s.Completed && d.Active
// Key and values used for grouping (note, you don't really need the
// value here, because you only need Count of the values in a group, but
// in case you needed anything from 's' or 'd' in 'select', you'd write this
let value = new { s, d }
let key = new { d.ID, d.FirstName, d.LastName }
group value by key into g
// Now, filter the created groups (return only non-empty) and select
// information for every group
where g.Count() > 0
select { ID = g.Key.ID, FirstName = g.Key.FirstName,
LastName = g.Key.LastName, Count = g.Count() };
The HAVING clause is translated to an ordinary where that is applied after grouping values using group ... by. The result of grouping is a collection of groups (another collections), so you can use where to filter groups. In the select clause, you can then return information from the key (used for grouping) and aggregate of values (using g.Count())
EDIT: As mmcteam points out (see comments), the where g.Count() > 0 clause is not necessary, because this is already guranteed by the join. I'll leave it there, because it shows how to translate HAVING clause in general, so it may be helpful in other cases.
Here's how I'd do it. Please note that I'm accustomed to linqtosql and am unaware if there are differences for the query in linqtoentities.
var query =
from d in myObjectContext.tbldesigner
where d.ACTIVE == 1
let manys =
from s in d.tbldesign
where s.COMPLETED == 1
select s
where manys.Count() > 0
select new
{
d.ID, d.FIRST_NAME, d.LAST_NAME,
DesignCount = manys.Count()
};
Ignoring the s.id which is confusing me (see my comment on the question), this is a simple query which would generate a having clause. Of course, in this case it's a worthless example since the count will always be more than 0 in this case.
Anyways, if you are using SQL to Entities, you should use the entity mapping to access the foreign key relationships instead of manually doing a join or a subquery.
var results = from d in db.tbldesigner
where d.TBLDESIGN.COMPLETED && d.ACTIVE
group d by new {d.ID, d.FIRST_NAME, d.LAST_NAME} into g
where g.Count() >= 0
select new {
d.ID, d.FIRST_NAME, d.LAST_NAME,
Count = g.Count()
};
NOTE: This is untested (and uncompiled) so there might be some issues, but this is where I would start.