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;
Related
I have below code that returns all the columns in student.
But I want to return only one column. Any solution?
IEnumerable<DataRow> x = from student in dt.AsEnumerable()
join d in dt1.AsEnumerable() on student.Field<string>("Name") equals d.Field<string>("LapName")
where d.Field<string>("LapName") == "HP"
select student;
You need to specify the column(s) you require in the select, in your case, something like this:
IEnumerable<string> x = from student in dt.AsEnumerable()
join d in dt1.AsEnumerable() on student.Field<string>("Name") equals d.Field<string>("LapName")
where d.Field<string>("LapName") == "HP"
select student.Field<string>("Name");
Note that the return type for x is now IEnumerable of string instead of DataRow.
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 two linq - sql queries, and im wondering how to join them..
First Query
var ab = from a in Items_worker.getCEAItems()
where a.ProjectCode == lbl_projectCode.Text
select new
{
a.ID
};
Second Query
var j = from c in tblInc_worker.get(c => c.MarginID == MarginID && c.IncTypeID == "CAPEX")
orderby c.DateCreated
select c.ID;
First Query would return:
fasf-1212-1212-1212-1212
afaa-1414-1414-1414-1414
Second Query would return:
fasf-1212-1212-1212-1212
afaa-1414-1414-1414-1414
0000-0000-0000-0000-0000
1111-1111-1111-1111-1111
question is how can i possibly join the two table. Wherein the second query should return all of the records with the same ID found in the first query plus the id containing "0000-0000-0000-0000-0000" second query..
The result should be:
fasf-1212-1212-1212-1212
afaa-1414-1414-1414-1414
0000-0000-0000-0000-0000
You can use union to join the both queries, for example split your second query in two with conditions like :
var ab = from a in Items_worker.getCEAItems()
where a.ProjectCode == lbl_projectCode.Text
select new
{
a.ID
};
var j = from c in tblInc_worker.get(c => c.MarginID == MarginID && c.IncTypeID == "CAPEX")
orderby c.DateCreated
select c.ID where c.ID.Equals("0000-0000-0000-0000-0000");
var j1 = from c in tblInc_worker.get(c => c.MarginID == MarginID && c.IncTypeID == "CAPEX")
orderby c.DateCreated
select c.ID where !(c.ID.Equals("0000-0000-0000-0000-0000"));
var result = ab.Union(j.Union(j1));
Hope this helps..
I need to write Join statment after writing query in linq
example :
var Query = (from Tab in Db.Employees
select Tab)
as i have some cases to perform join operation so
i need to do it on this Query Query.Join(Join with another Table like Department); I need the Syntax
if (DeptID != -1){ Query.Join(Join with table Department where FkDeptID = DeptID); }
Consider the usage of join in the LINQ 'query syntax':
from t1 in db.Table1
join t2 in db.Table2 on t1.field equals t2.field
select new { t1.field2, t2.field3}
Something like this?
var results = (from q in Query
join m in myList on q.SomeID = m.SomeID
select unknown);
Try using this query:
var Query =
from e in Db.Employees
join d in Db.Departments on e.FkDeptID equals d.DeptID into departments
select new
{
Employee = e,
Department = departments.SingleOrDefault(),
};
This works assuming that when e.FkDeptID == -1 that there is no record in the Departments table and in that case Department would be assigned null.
You should never have more than one department for an employee so I've used SingleOrDefault rather than FirstOrDefault.
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,
}
);