How can I write this HQL in Linq:
select a from A a
join a.childrenList b
where b = 1
childrenList is a list of enums which is not mapped to database by type but
rather is saved with its integer value.
This HQL works fine but I want to write it in Linq.
I cannot write something that can be compiled.
I think you can do
var results =
from a in db.Query<A>()
where a.childrenList.Any(b => b == (B)1)
select a;
or, using chained methods:
var results = db.Query<A>().Where(a => a.childrenList.Any(b => b == (B)1));
Regarding our comments above, I think you can drop the from A a in ... select a statements, because they are redundant.
Related
I want to have join query from a table with a dictionary based on a common field, my query is:
var query = from c in db.Exp
join d in lstUniprotDic on c.UniID equals d.Key
select new
{
c.UniID,
IdentityPercent=d.Value.ToString(),
c.PrId,
c.SpotNo
}
but i got the following error
Local sequence cannot be used in LINQ to SQL implementation of query operators except the Contains() operator.
That pretty much says it all. You can't use the dictionary in your LINQ to SQL query except when using Contains.
Solution:
(from c in db.Exp where lstUniprotDic.Keys.Contains(c.UniID) select c).AsEnumerable()
join d in lstUniprotDic on c.UniID equals d.Key
select new
{
c.UniID,
IdentityPercent=d.Value.ToString(),
c.PrId,
c.SpotNo
}
I am not sure if the usage of lstUniprotDic.Keys in the LINQ to SQL query is actually working.
If not, try using this code instead:
var ids = lstUniprotDic.Keys.ToArray();
(from c in db.Exp where ids.Contains(c.UniID) select c).AsEnumerable()
join d in lstUniprotDic on c.UniID equals d.Key
select new
{
c.UniID,
IdentityPercent=d.Value.ToString(),
c.PrId,
c.SpotNo
}
Here is the problematic line:
var originalSummaryCandidates =
(from a in masterDB.tbl_thirty_second_summaries_multi_variant_associations
join d in masterDB.tbl_thirty_second_summaries_multi_variants on a.ThirtySecSummaryId equals d.ThirtySecondSummaryId_this
where d.DrugId == drugId &&
variantGenotypeIds.Contains(new int[] {a.VariantId, a.GenotypeId})
select d.ThirtySecondSummaryId_this)
.Distinct()
.ToList();
variantGeotpeIds is of type List<int[]>. Both a.VariantId and a.GenotypeId are of type int.
I cannot figure out why it why it will not do the comparison. Is this a deferred execution issue? It doesn't seem like it should be...
Thanks in advance.
List<T>.Contains only takes a single parameter of type T. In your case, T is Int32 but you're passing in a Int32[].
If you want to check that both values are in the list, you have to break the calls apart:
where d.DrugId == drugId &&
variantGenotypeIds.Contains(a.VariantId) &&
variantGenotypeIds.Contains(a.GenotypeId)
EDIT
If variantGenotypeIds is actually a List<Int32[]>, then there's another issue. LINQ to SQL will try to convert your query into its SQL equivalent. In this case, there's no way to translate your query into SQL so LINQ to SQL will throw an Exception.
If you really need to query this way, you'll have to read the records into memory first and then query using LINQ to Objects (which may or may not be a big deal depending on how many rows you are reading):
var query =
from a in masterDB.tbl_thirty_second_summaries_multi_variant_associations
join d in masterDB.tbl_thirty_second_summaries_multi_variants
on a.ThirtySecSummaryId equals d.ThirtySecondSummaryId_this
where d.DrugId == drugId
select new { a, d }
var originalSummaryCandidates =
(from q in query.AsEnumerable()
where variantGenotypeIds.Contains(new [] { q.a.VariantId, q.a.GenotypeId})
select d.ThirtySecondSummaryId_this)
.Distinct()
.ToList();
Array comparison uses reference equality by default. It's possible that linq-to-sql just tries to translate that into SQL that compares the values, but you'd have to look at the generated SQL to be sure. Another option would be to use Any instead:
where d.DrugId == drugId &&
variantGenotypeIds.Any(v => v[0] == a.VariantId && v[1] == a.GenotypeId)
but I'm not sure if Linq-to-Sql will be able to translate that to the correct SQL either. Another option would be to project the List` to a > and then do a string comparison:
variantGenotypeStrings = variantGenotypeIds.Select(v => string.Format("{0}|{1}", v[0],v[1]);
var originalSummaryCandidates =
(from a in masterDB.tbl_thirty_second_summaries_multi_variant_associations
join d in masterDB.tbl_thirty_second_summaries_multi_variants on a.ThirtySecSummaryId equals d.ThirtySecondSummaryId_this
where d.DrugId == drugId &&
variantGenotypeStrings.Contains(string.Format("{0}|{1}", a.VariantId, a.GenotypeId))
select d.ThirtySecondSummaryId_this)
.Distinct()
.ToList();
I want to filter my LINQ query based on an included table but am having some trouble.
Here is the original statement, which works:
return
this.ObjectContext.People.
Include("Careers").
Include("Careers.Titles").
Include("Careers.Titles.Salaries");
Now I'm trying to filter on Careers using projected filtering but am having trouble. It compiles but it leaves out the Titles and Salaries tables, which causes runtime errors, and I can't seem to add those tables back in:
var query1 = (
from c in
this.ObjectContext.People.
Include("Careers").
Include("Careers.Titles").
Include("Careers.Titles.Salaries")
select new
{
c,
Careers = from Careers in c.Careers
where Careers.IsActive == true
select Careers
});
var query = query1.AsEnumerable().Select(m => m.c);
return query.AsQueryable();
How can I include the titles and salaries tables in the filtered query?
You can simplify your query considerably, which should resolve your issue. I'm assuming that you want all people with at least 1 active career:
var query =
from c in
this.ObjectContext.People.
Include("Careers").
Include("Careers.Titles").
Include("Careers.Titles.Salaries")
where c.Careers.Any(c => c.IsActive);
return query;
I would try something like,
var query = from p in ObjectContext.People
join c in ObjectContext.Careers on p equals c.Person
where c.IsActive
select p;
Let say i have the following schema
Content(Id, ....)
TagContent(TagId, ContentId)
Tag(TagId, Name)
Suppose I'd like to select all content records that have tag with name "test".
In SQL I would write:
select Content.Id
from Content
join TagContent as TC on (TC.ContentId = Content.Id)
Join Tag on (TC.TagId = Tag.Id)
where Tag.Name = 'Test'
Could you suggest how to write a similar query in Linq if you have only Table available?
(I'd like to create an extension method Content.ByTag('tag') -> IQueryable )
I've only managed to create a query that use the sql exists statement instead of join.
Which means that the queries are extremely inefficient.
My current inefficient solution looks as follows:
DataContext.Contents.Where(c => c.TagContents.Any(tc => tc.Tag.Name == "Test"))
NOTE:
As I'd like to make the extension method on DataContext.Contents I won't have access to other tables that is DataContext.Tag and DataContext.ContentTag.
Something like this perhaps
var contentIds = from c in Content
join tc in TagContent on c.Id equals tc.ContentId
join t in Tag on tc.TagId equals t.Id
where t.Name == "Test"
select new
{
ContentId = c.Id
};
I'm trying to write some LINQ To SQL code that would generate SQL like
SELECT t.Name, g.Name
FROM Theme t
INNER JOIN (
SELECT TOP 5 * FROM [Group] ORDER BY TotalMembers
) as g ON t.K = g.ThemeK
So far I have
var q = from t in dc.Themes
join g in dc.Groups on t.K equals g.ThemeK into groups
select new {
t.Name, Groups = (from z in groups orderby z.TotalMembers select z.Name )
};
but I need to do a top/take on the ordered groups subquery. According to http://blogs.msdn.com/vbteam/archive/2008/01/08/converting-sql-to-linq-part-7-union-top-subqueries-bill-horst.aspx in VB I could just add TAKE 5 on the end, but I can't get this syntax to work in c#. How do you use the take syntax in c#?
edit: PS adding .Take(5) at the end causes it to run loads of individual queries
edit 2: I made a slight mistake with the intent of the SQL above, but the question still stands. The problem is that if you use extension methods in the query like .Take(5), LinqToSql runs lots of SQL queries instead of a single query.
Second answer, now I've reread the original question.
Are you sure the SQL you've shown is actually correct? It won't give the top 5 groups within each theme - it'll match each theme just against the top 5 groups overall.
In short, I suspect you'll get your original SQL if you use:
var q = from t in dc.Themes
join g in dc.Groups.OrderBy(z => z.TotalMembers).Take(5)
on t.K equals g.ThemeK into groups
select new { t.Name, Groups = groups };
But I don't think that's what you actually want...
Just bracket your query expression and call Take on it:
var q = from t in dc.Themes
join g in dc.Groups on t.K equals g.ThemeK into groups
select new { t.Name, Groups =
(from z in groups orderby z.TotalMembers select z.Name).Take(5) };
In fact, the query expression isn't really making things any simpler for you - you might as well call OrderBy directly:
var q = from t in dc.Themes
join g in dc.Groups on t.K equals g.ThemeK into groups
select new { t.Name, Groups = groups.OrderBy(z => z.TotalMembers).Take(5) };
Here's a faithful translation of the original query. This should not generate repeated roundtrips.
var subquery =
dc.Groups
.OrderBy(g => g.TotalMembers)
.Take(5);
var query =
dc.Themes
.Join(subquery, t => t.K, g => g.ThemeK, (t, g) => new
{
ThemeName = t.Name, GroupName = g.Name
}
);
The roundtrips in the question are caused by the groupjoin (join into). Groups in LINQ have a heirarchical shape. Groups in SQL have a row/column shape (grouped keys + aggregates). In order for LinqToSql to fill its hierarchy from row/column results, it must query the child nodes seperately using the group's keys. It only does this if the children are used outside of an aggregate.