I have the SQL query
with c as (
select categoryId,parentId, name,0 as [level]
from task_Category b
where b.parentId is null
union all
select b.categoryId,b.parentId,b.name,[level] + 1
from task_Category b join c on b.parentId =
c.categoryId)
select name,[level],categoryId,parentId
as item
from c
and I want to convert it to LINQ to SQL, yet my LINQ skills are not there yet. Could someone please help me convert this. It's the with and union statements that are making this a bit more complex for me.
Any help appreciated.
That is a recursive CTE. LINQ to SQL does not support recursive CTEs yet (and probably never will). Sorry!
As a workaround you can leave the query as it is in SQL and put it in a stored procedure. You can then call that stored procedure from LINQ to SQL.
LINQ-to-SQL only supports basic queries; CTE and recursion are not included in this. Therefore, here's my high-tech translation to LINQ-to-SQL:
var data = ctx.ExecuteQuery<MyStub>(#"
with c as (
select categoryId,parentId, name,0 as [level]
from task_Category b
where b.parentId is null
union all
select b.categoryId,b.parentId,b.name,[level] + 1
from task_Category b join c on b.parentId =
c.categoryId)
select name,[level],categoryId,parentId
as item
from c").ToList();
with
class MyStub {
public string name {get;set;}
public int level {get;set;}
public int categoryId {get;set;}
public int parentId {get;set;}
}
Related
I'm trying to convert the following MySQL statement in to LINQ query format
SELECT * FROM table1 WHERE table1.id IN (SELECT c_id FROM table2 WHERE a_id IN (1, 49) GROUP BY c_id HAVING COUNT(*) = 2) ORDER BY name
Got as far as this, but I'm drawing a blank on how to handle the IN and 2nd SELECT statement
myItems = from c in table1
let id = c.id
where ????
orderby c.name
select c;
Would appreciate some guidance with this please
Try this:
var ids=new[]{1,49};
var innerquery=table2.Where(e=>ids.Contains(e.a_id))
.GroupBy(e=>e.c_id)
.Where(g=>g.Count()==2)
.Select(g=>g.Key);
var myItems = from c in table1
where innerquery.Contains(c.id)
orderby c.name
select c;
First define your inner query,after the group by you will get a collection of IGrouping<TKey, TElement>> that represent a collection of objects that have a common key, filter the groups choosing only those where count==2, and select the keys of those groups. The second part is really easy to understand. I split the process in two queries to do it more readable, but you can merge both query in one.
I am writing a simple LINQ query. Table structure is defined below:
Table A
Id int,
VName varchar2(20),
VAddress varchar2(200)
Table B
Id int,
NName varchar2(20),
NAddress varchar2(200)
LINQ Query
from c in A
join x in B on c.Id equals x.Id
order by A.Id
select New{
c.Id,
x.NName
}
Then SQL Generate as
select Filter1.Id,Filter1.NName from(
Select Extend1.Id,Extend1.VName,Extend1.VAddress,
Extend2.Id as Id1,Extend2.NName,Extend2.NAddress
from A as Extend1 Inner Join B as Extend2 on Extend1.Id=Extend2.ID)
as Filter1
MY Problem: I don't want select many columns in SubQuery.
If you're really worried about performance, then just use plain SQL... it's just about always faster than Linq (in my personal experience). Also, you can try using this Linq to execute your SQL:
IEnumerable<YourDataType> result = DataContext.ExecuteQuery<YourDataType>(SqlString);
You can find out more from the DataContext.ExecuteQuery<TResult> Method (String, Object\[\]) page at MSDN. Please note that this page relates to a different overload of this method, but it has examples in it.
I have this query in Sql Server which I need to consume in EntityFramework, So how can I write a EntityFramwork code which will have the same result as this
WITH cte AS
(
SELECT *
FROM StockGroups
WHERE GroupParent ='Stationery'
UNION ALL
SELECT g.*
FROM StockGroups g
JOIN cte
ON g.GroupParent = cte.GroupName
)
SELECT *
FROM cte
I don't know how to convert it in EF, so I tried with join.
from a in db.StockGroups
join b in db.StockGroups on new { GroupParent = a.GroupParent } equals new { GroupParent = b.GroupName }
where
b.GroupName == "Stationery"
select new {
a.GroupName,
a.GroupParent,
Column1 = b.GroupName,
Column2 = b.GroupParent
}
But the result is not same, as recursive as CTE.
EF does not support recursive CTE's. Use a view or a table valued function.
Getting input from the other experts over SO, I have come up with my own way to achieve this.
IEnumerable<StockGroup> sg = dbContext.ExecuteStoreQuery<StockGroup>(
#"WITH q AS
(
SELECT *
FROM LedgerGroups
WHERE GroupParent = 'Customers'
UNION ALL
SELECT m.*
FROM LedgerGroups m
JOIN q
ON m.GroupParent = q.GroupName
)
SELECT *
FROM q
");
You cannot use CTE recursion in Entity Framework.
Use stored procedure and call that stored procedure through EF
I dont think there is support for recursive CTEs in LINQ nor in EF. The solution is to expose the CTE as a view. The article on Recursive or hierarchical queries using EF Code First and Migrations shows how to deploy such a view using EF code first migrations. Recursive or hierarchical queries using EF Code First and Migrations
Original source:
https://stackoverflow.com/a/11929928/3850405
Is it posible in NHibernate to create a query that looks like this?
select hi.ContactId
From dbo.vw_HostInterests hi INNER JOIN
( Select cm1.ContactId
From dbo.vw_ContactMoments cm1 INNER JOIN
(
Select Contactid
From dbo.vw_ProfileNaw
where GenderId = 1000
) as pn1 on cm1.ContactId = pn1.ContactId
where cm1.ActivityId = 1001
)as cm on hi.ContactId = cm.ContactId
where hi.ActivityId = 1038
I've managed to create the correct output with the IN statement, but I'd realy like the SQL to look like this.
The Criteria below shows part of above query with the IN Statement I used (but want to replace):
ICriteria criteria = DbSession.CreateCriteria<Contact>();
var dCriteria1 = DetachedCriteria.For(typeof(VwHostInterest))
.Add(Expression.Eq("ActivityId", 1038))
.SetProjection(Projections.ProjectionList()
.Add(Projections.GroupProperty("ContactId")));
var dCriteria2 = DetachedCriteria.For(typeof(VwContactMoment))
.Add(Expression.Eq("ActivityId", 1001))
.SetProjection(Projections.ProjectionList()
.Add(Projections.GroupProperty("ContactId")));
criteria.Add(Subqueries.PropertyIn("ContactId", dCriteria1));
criteria.Add(Subqueries.PropertyIn("ContactId", dCriteria2));
int count = (Int32)criteria
.SetProjection(Projections.Count("ContactId"))
.UniqueResult();
Probably not the answer you are looking for and apologies if it isn't but my experience is that your best bet with such complex queries would be to:
a) Do this whole thing as a view and map it in NHibernate
b) Create the inner select as a view and create a mapping such that you can relate it in your query
b) Or override nhibernate (override as in skip and not in OO terms ;) and write this as a named query using native SQL.
Does that nested query produce the same result as the following?
SELECT hi.ContactId
FROM dbo.vw_HostInterests hi
INNER JOIN vw_ContactMoments cm1 on hi.ContactId = cm1.ContactId
AND cm1.ActivityId = 1001
INNER JOIN dbo.vw_ProfileNaw pn1 on pn1.ContactId = cm1.ContactId
AND pn1.GenderId = 1000
WHERE hi.ActivityId = 1038
This is my sql query: subsonic version 2.1.0.0 No Linq (.net 2.0)
select
(
select Title from MenuTranslation mnu2 where
mnu2.languageid = 1 and mnu2.menuelementid = menutranslation.menuelementid
)as BaseTitle, *
from menutranslation
inner join menuelement on menuelement.id = menutranslation.menuelementid
where menuelementid
in (select id from menuelement where parentid = 4)
and languageid = 2
Not at this time - however you can run IN queries with a SELECT - not subqueries however.
You would need to use the inlineQuery class where you generate the sql yourself to accomplish what you are going after