I'm brand new to .net MVC, and while I have some basic experience with writing SQL queries, I'm not sure how to go about what I need to do for .NET.
My initial query looks like this:
var results = (from s in db.Members
join sa in db.FocusArea on s.ID equals sa.MemberID
where sa.Area == SearchString
select new { s.ID, s.Name, s.Overview }).ToList();
This is not functioning correctly. It is seaching in the s.Overview for some reason. And, I need to make this query much more complicated. In short, I have three tables I need to search across. And with this query, it is not working:
var conceptResults = (from s in db.Cohorts
join oa in db.OutcomeArea on s.ID equals oa.CohortID
where ((oa.Area.Contains(SearchString))
|| (oa.OutcomeType.Contains(SearchString)))
select new { s.ID, s.Name, s.Overview }).ToList();
I need to use my SearchString to search for matches in both Area and Description in db.FocusArea.
I also need to use my SearchString to search for matches (contains) in another table db.SpecificFocusAreas for column SFocusArea where again the join is the ID/MemberID.
Is there a way to essentially do a join or join type of statement? I don't want to join all three tables because I am looking for results from either of the two joins, not from all joins.
Related
I am trying to get all data from the join table to data review, but what I learn is just to specify the attributes one by one in the SELECT statement as following code:
var query = (from inv in db.tblinventories
join sup in db.tblsuppliers on inv.SupplierID equals sup.SupID into left
from sup in left.DefaultIfEmpty()
select new { inv.Invnum,inv.Model, sup.name }).ToList();
this.dgvPOS.DataSource = query;```
Is this the only way to fetch all data? Because in ORACLE SQL the way is quite simple by using "*" to represent all attributes like this:
SELECT *
FROM tblinventories
LEFT JOIN tblsuppliers
ON tblinventories.SupplierID = tblsuppliers.SupID;
In my database, each URI has associated tags (Tag table) and each pageview (PageView table) is associated with someone viewing a particular page. I want to return a list of URIs that have the same tags as a given URI, by count of each URI that shares those tag(s). My SQL query looks like this:
select count(URI) as 'Count', p.URI, t.Name
from tracking.PageView as p
inner join Tracking.Tag as t on p.ID = t.PageViewID
where t.name in
(select t.Name
from tracking.PageView as p
inner join Tracking.Tag as t on p.ID = t.PageViewID
where p.URI = 'URI WE WANT TAGS OF'
)
and p.uri like '%/articles/%'
group by p.URI , t.name
order by Count desc
My apologies if the description is too vague for the query or if the query itself is rough. It was just the first one that worked. I've tried to separate the subquery into a variable and select values in that subquery, but it's been some time since I've used LINQ and I'm spinning wheels at this point.
The following is pretty much an exact translation of your current SQL query, which should get you started.
from p in tracking.PageView
join t in Tracking.Tag on p.ID equals t.PageViewID
where p.uri.Contains("/articles/")
&& (
from p2 in tracking.PageView
join t2 in Tracking.Tag on p2.ID equals t2.PageViewID
where p2.URI == "URI WE WANT TAGS OF"
select t2.name
).Contains(t.name)
group new { p, t } by new { p.URI, t.name } into g
orderby g.Count() descending
select new {
Count = g.Count(),
g.Key.URI,
g.Key.Name
}
I'm a junior developer and trying to convert the following linq statement to T-SQL:
var items = from u in DataContext.Users_SearchUsers(searchPara.UserFirstName,
searchPara.UserLastName,
searchPara.UserEmailAddress,
fetchOptions.page,
fetchOptions.rp,
fetchOptions.sortname,
fetchOptions.sortorder)
.ToList()
join a in DataContext.UserAccesses
.Where(x => x.Access.AccessTypeId == 4).ToList() on u.UserID equals a.UserId into accessGroup
select new {};
Can one please help me ? into accessGroup ---> (very important)
First of all you need to understand where your data is coming from. You are loading information from Users_SearchUsers on the one hand and UserAccesses on the other hand. The first query looks like
select <somecolumns>
from users
where <somefilters>;
(you need to use your actual columns and criteria, but Users_SearchUsers is not specified in the question at all). I have ignored paging here for the sake of simplicity
The second query looks like this:
select *
from user_accesses
where access_type_id = 4;
Let's join the two:
select <someoutercolumns>
from
(
select <someinnercolumns>
from users
where <somefilters>
) t1
join
(
select <someotherinnercolumns>
from user_accesses
where access_type_id = 4
) t2
on t1.user_id = t2.user_id;
These queries are probably not the exact solutions you need, but you want the answers to improve, then improve your question.
The requirement makes sense if the LINQ query is very slow. In that case you will need to refactor it in the following manner:
select <somecolumns>
from users
join user_accesses
on users.user_id = user_accesses.user_id and user_accesses.access_type_id = 4
where <somefilters>;
you can use this code
select *(you can put your columns instead *)
from Users
join UserAccesses
on Users.userid = UserAccesses.userid
where UserAccesses.typeid = 4;
This is my Query in SQL :
Select distinct * from tr.Table1
Left Outer join tr.Table2 on tr.Table1.ID = tr.Table2.ID
Left Outer join tr.Table3 on tr.Table2.AId= tr.Table3.ID
where tr.Table1.Deleted =1 and tr.Table1.Ready=1 and tr.Table1.Show=0
The query is working in SQL and gives the expected results.The thing here is that I want the equivalent of this using LINQ. I have tried some variations in LINQ queries such as :
var query = from p in _ctx.Table1
join s in _ctx.Table2 on p.Id equals s.Id into bag1
from to in bag1.DefaultIfEmpty()
join tx in _ctx.Table3 on to.AId equals tx.Id into bag2
from ts in bag2.DefaultIfEmpty()
select new
{
ContactNo = to.Table1.ContactNo
};
But it always doesn't return all the field values. Some are returned as NULL. Also tried referring to some other link as well but they all focus on joining with the parent table whereas I have to join one of the joined tables with the other one. So here I am, struggling with this.
This is the output that I'm getting as of now. Some values are null. The field has values but due to some joining issue, they are returned as NULL.
Guidance here is appreciated. Thank you.
Your query looks fine to me, the reason why you must be getting the Nulls is because when we use DefaultIfEmpty, it returns null for non-matching rows, thus you need to handle that while fetching the actual results. Try doing something like this:-
var query = from p in _ctx.Table1
join s in _ctx.Table2 on p.Id equals s.Id into bag1
from to in bag1.DefaultIfEmpty()
join tx in _ctx.Table3 on to.AId equals tx.Id into bag2
from ts in bag2.DefaultIfEmpty()
select new
{
ContactNo = to == null ? String.Empty : to.Table1.ContactNo
};
Assuming, ContactNo to be of type String, I have used String.Empty you can use any default value.
Hi im kinda new to linq to sql I know about the basics. The problem is I want to do a left join in a query. There are 3 tables in the query.
Claimants ( all rows should be returned from this table)
Claim
User
The query should return all Users who have Claimants. This is done through the many to many table Claim. But regardless of Users all Claimants should be returned. Thus the left join on Claimants.
I have the following query
var d = (from Claimants in DB.Claimants
join Claims in DB.Claims on Claimants.Claiment_ID equals Claims.Claiment_ID
join Users in DB.Users on Claims.User_ID equals Users.User_ID
where (Claimants.TrialDate.Value >= dtDayStart & Claimants.TrialDate <= dtDayEnd)
select new
{
ClaimantFirstName = Claimants.FirstName,
ClaimantLasname = Claimants.LastName,
ClaimantsID = Claimants.IDNumber,
Claimants.OurReference,
Claimants.TrialDate,
InterviewStart = Claims.DateTimeStart,
InterviewEnd = Claims.DateTimeEnd,
Claims.Priority,
UserFirstname = Users.FirstName,
UserLastName = Users.LastName,
UserID = Users.IDNumber
});
I have tried using an into statement as follows but with no luck
var d = (from Claimants in DB.Claimants
join Claims in DB.Claims on Claimants.Claiment_ID equals Claims.Claiment_ID
into TheClaimants
from Claims in TheClaimants.DefaultIfEmpty()
join Users in DB.Users on Claims.User_ID equals Users.User_ID
where (Claimants.TrialDate.Value >= dtDayStart & Claimants.TrialDate <= dtDayEnd)
select new
{
ClaimantFirstName = Claimants.FirstName,
ClaimantLasname = Claimants.LastName,
ClaimantsID = Claimants.IDNumber,
Claimants.OurReference,
Claimants.TrialDate,
InterviewStart = Claims.DateTimeStart,
InterviewEnd = Claims.DateTimeEnd,
Claims.Priority,
UserFirstname = Users.FirstName,
UserLastName = Users.LastName,
UserID = Users.IDNumber
});
I would appreciate it if someone could point me in the right direction as to how to use these joins left right correctly and explain how the work. Thank you very much in advance.
var d = (from Claimants in DB.Claimants
join Claims in DB.Claims on Claimants.Claiment_ID equals Claims.Claiment_ID)
.DefaultIfEmpty()
join Users in DB.Users on Claims.User_ID equals Users.User_ID
where (Claimants.TrialDate.Value >= dtDayStart & Claimants.TrialDate <= dtDayEnd)
.DefaultIfEmpty()
select new
{
ClaimantFirstName = Claimants.FirstName,
ClaimantLasname = Claimants.LastName,
ClaimantsID = Claimants.IDNumber,
Claimants.OurReference,
Claimants.TrialDate,
InterviewStart = Claims.DateTimeStart,
InterviewEnd = Claims.DateTimeEnd,
Claims.Priority,
UserFirstname = Users.FirstName,
UserLastName = Users.LastName,
UserID = Users.IDNumber
});
Left outter join
You must know a Luan. If you want all the Claiments to return start by selecting from Claiments and then left join onto the other tables.
Try the following :
LINQ to SQL Left Outer Join
In LINQ, the ".Join()" extension method is the equivalent of SQL inner join.
For outer joins you have to use the ".GroupJoin()" extension method.
Assuming you know the .Join well, the GroupJoin is simple to use. I have to admit that when I first needed to do an outer join in LINQ it was damn hard to find out. I cannot fanthom why did they call it like that.
Although in VB.Net, here's an article that presents various SQL constructs translated into LINQ syntax, even if in VB, still easy to convert to extension methods: http://blogs.msdn.com/b/vbteam/archive/2007/12/31/converting-sql-to-linq-part-6-joins-bill-horst.aspx?Redirected=true
EDIT: #DavidB posted in his comments a much better solution, but only if you can use some ORM navigational properties. If you don't have them, then GroupJoin is probably the most reasonable