How can I write a linq to entities query that includes a having clause?
For example:
SELECT State.Name, Count(*) FROM State
INNER JOIN StateOwner ON State.StateID = StateOwner.StateID
GROUP BY State.StateID
HAVING Count(*) > 1
Any reason not to just use a where clause on the result?
var query = from state in states
join stateowner in stateowners
on state.stateid equals stateowner.stateid
group state.Name by state.stateid into grouped
where grouped.Count() > 1
select new { Name = grouped.Key, grouped.Count() };
I believe you can use a GroupBy followed by a Where clause and it will translate it as a Having. Not entirely sure though.
If you want to compare a variable that is not in the group by (Ex: age), then it would be:
var duplicated = (
from q1 in db.table1
where (q1.age >= 10 )
group q1 by new { q1.firstName, q1.lastName } into grp
where (grp.Count() > 1 )
select new
{
firstName= grp.Key.firstName,
lastName = grp.Key.lastName,
}
);
Related
i plan to join 2 table, and get the distinct value of language column. How should i achieve that in Linq? I try add 'group' but no luck. Besides, i want to select s value too together with r distinct language value.
My code:
public ActionResult QuestionLink(int Survey_ID)
{
var query = from r in db.SURV_Question_Ext_Model
join s in db.SURV_Question_Model
on r.Qext_Question_ID equals s.Question_ID
where s.Question_Survey_ID == Survey_ID
group r.language << this is not work **
select r;
return PartialView(query.ToList());
}
This is what in MoreLinq is called DistinctBy. But if that method works on IEnumerable, so you can't use it in an EF query. But you can use the same approach:
var query = from r in db.SURV_Question_Ext_Model
join s in db.SURV_Question_Model on r.Qext_Question_ID equals s.Question_ID
where s.Question_Survey_ID == Survey_ID
group new { r, s } by r.language into grp
select grp.FirstOrDefault();
But I wonder if this really is what you want. The result depends on the ordering of languages that the database happens to return. I think you should add a predicate for a specific language and remove the grouping:
var query = from r in db.SURV_Question_Ext_Model
join s in db.SURV_Question_Model
on r.Qext_Question_ID equals s.Question_ID
where s.Question_Survey_ID == Survey_ID
&& r.language == someVariable
select new { r, s };
You can do like this:
var query = from r in db.SURV_Question_Ext_Model
join s in db.SURV_Question_Model
on r.Qext_Question_ID equals s.Question_ID
where s.Question_Survey_ID == Survey_ID
group new {r, s} by r.language into rg
select rg.Key;
I want to make this query in linq to sql .
Please help. I am new to linq and having problem to with the group by clause .
Here is the sql query
select count(USERID), d.DEPTNAME from USERS u
join department d on u.DEPTID = d.DEPTID
group by u.DEPTID, d.DEPTNAME
A more direct translation would be like this:
var query =
from u in db.Users
join d in db.Departments on u.DeptId equals d.DeptId
group d by new { d.DeptId, d.DeptName } into g
select new
{
g.Key.DeptName,
Count = g.Count(),
};
Though I think it would be better off written like this:
// looks like we're counting users in each department
var query =
from d in db.Departments
select new
{
d.DeptName,
Count = db.Users.Count(u => u.DeptId == d.DeptId),
};
Linq is brand new to me so I apologize if this is really stupid.
I am trying to get the count from a multi-table join with where clause, without group by. I've seen examples of group by and will resort to that if need be, but I am wondering if there is a way to avoid it. Is sql my query would look something like this;
SELECT Count(*)
FROM plans p
JOIN organizations o
ON p.org_id = o.org_id
AND o.deleted IS NULL
JOIN orgdata od
ON od.org_id = o.org_id
AND od.active = 1
JOIN orgsys os
ON os.sys_id = od.sys_id
AND os.deleted IS NULL
WHERE p.deleted IS NULL
AND os.name NOT IN ( 'xxxx', 'yyyy', 'zzzz' )
What's the best way to get this?
All you need is to call Count(). You're only counting the number of results. So something like:
var names = new[] { "xxxx", "yyyy", "zzzz" };
var query = from plan in db.Plans
where plan.Deleted == null
join organization in db.Organizations
on plan.OrganizationId equals organization.OrganizationId
where organization.Deleted == null
join orgData in db.OrganizationData
on organization.OrganizationId equals orgData.OrganizationId
where orgData.Active == 1
join os on db.OrganizationSystems
on orgData.SystemId equals os.SystemId
where os.Deleted == null &&
!names.Contains(os.Name)
select 1; // It doesn't matter what you select here
var count = query.Count();
I want to join the following Tables
1. B_Book[1st Table]
-B_BID (Book ID)(PK)
-B_Name
-B_CategroyID (FK)
2. BI_BookInstance [2nd Table]
-BI_IID(Instance ID)
-BI_BID (FK)
-BI_Price
3. BC_BookCategory [3rd Table]
-BC_CategoryID (PK)
-BC_CategoryName
First Join B_Book and BI_BookInstance then join the result of those both with BookCategory.
(1st join)[B_BID equals BI_BID]
(2nd nested join)[result of 1st join B_CategoryID equals BC_CategoryID]
Edit
SQL would be something like the following:
SELECT * FROM
(SELECT * FROM B_Book b JOIN BI_BookInstance bi on b.B_BID = bi.BI_BID) as t1
JOIN BC_BookCategoryID bc on bc.BC_CategoryID = t1.B_CategoryID
What matches your query in LINQ would be the following (and you'll notice the similarity with SQL). I've also included some examples on how to rename the fields returned, such as Price or CategoryName:
var results = from b in B_Book
join bi in BI_BookInstance
on b.B_BID equals bi.BI_BID
join bc in BC_BookCategory
on b.B_CategoryID equals bc.BC_CategoryID
select new
{
// put in whatever fields you want returned here:
b.B_BID,
b.B_CategoryID,
b.B_Name,
bi.BI_BID,
bi.BI_IID,
Price = bi.BI_Price,
bc.BC_CategoryID,
CategoryName = bc.BC_CategoryName
};
I have supposed inner joins (your FKs is not null), so i would like query like this:
var ctx = new YourEntities();
var query = from b in ctx.B_Book
from bi in ctx.BI_BookInstance
from bc in ctx.BC_BookCategory
where b.B_BID == bi.BI_BID && b.B_CategoryID == bc.BC_CategoryID
select new
{
BInstID = bi.BI_IID,
BName = b.B_Name,
BPrice = bi.BI_Price,
BCategory = bc.BC_CategoryName
};
foreach (var item in query)
{
Console.WriteLine(item.BInstID);
Console.WriteLine(item.BName);
Console.WriteLine(item.BPrice);
Console.WriteLine(item.BCategory);
Console.WriteLine("");
}
You can do this without explicitly using linq's join statement, provided that navigation properties are in place:
from b in ctx.B_Book
from bi in b.BookInstances
select new { b.Property1, bi.Property2, b.BookCategory.Name }
I have the following view:-
CREATE VIEW tbl_adjudicator_result_view
AS
SELECT a.adjudicator_id, sar.section_adjudicator_role_id, s.section_id, sdr.section_dance_role_id, d.dance_id, c.contact_id,
ro.round_id, r.result_id, c.title, c.first_name, c.last_name, d.name, r.value, ro.type
FROM tbl_adjudicator a
INNER JOIN tbl_section_adjudicator_role sar on sar.section_adjudicator_role2adjudicator = a.adjudicator_id
INNER JOIN tbl_section s on sar.section_adjudicator_role2section = s.section_id
INNER JOIN tbl_section_dance_role sdr on sdr.section_dance_role2section = s.section_id
INNER JOIN tbl_dance d on sdr.section_dance_role2dance = d.dance_id
INNER JOIN tbl_contact c on a.adjudicator2contact = c.contact_id
INNER JOIN tbl_round ro on ro.round2section = s.section_id
LEFT OUTER JOIN tbl_result r on r.result2adjudicator = a.adjudicator_id AND r.result2dance = d.dance_id
When I run the following query directly against the db I get 0 in the count column where there is no result
select adjudicator_id, first_name, COUNT(result_id)
from tbl_adjudicator_result_view arv
where arv.round_id = 16
group by adjudicator_id, first_name
However when I use LINQ query I always get 1 in the Count Column
var query = from arv in db.AdjudicatorResultViews
where arv.round_id == id
group arv by new { arv.adjudicator_id, arv.first_name} into grp
select new AdjudicatorResultViewGroupedByDance
{
AdjudicatorId = grp.Key.adjudicator_id,
FirstName = grp.Key.first_name,
Count = grp.Select(p => p.result_id).Distinct().Count()
};
What do I need to change in the View / Linq query.
You're not doing the same thing in the LINQ query as in the SQL. COUNT(result_id) does not count distinct values of result_id - it counts non-null values.
Try this instead:
Count = grp.Select(p => p.result_id).Where(x => x != null).Count()
The point is: you're grouping your data in the LINQ query - and you'll always get at least one group.
That group's Count may be 0 - but the count of groups will be 1.