I'd like to group my request by FkOperateur and FkPstStd but I still need information in the select new part. How should I proceed to get IdPoste, FkStandard, IsValidated, Date depending on the group part result
var shortFormations =
(from f in _context.Formations
where f.FkPstStdNavigation.FkPosteNavigation.FkZoneNavigation.FkBatimentNavigation.IdBatiment == Batiment && (f.FkOperateurNavigation.Equipe == Equipe || Equipe == null)
group f by new { f.FkOperateur, f.FkPstStd } into formation
select new shortFormations
{
FkOperateur = formation.Key.FkOperateur,
FkPstStd = formation.Key.FkPstStd,
IdPoste = f.FkPstStdNavigation.FkPosteNavigation.IdPoste,
FkStandard = f.FkPstStdNavigation.FkStandard,
IsValidated = f.IsValidated,
Date = f.DateFormation,
})
.AsNoTracking()
.ToList();
I can't get IdPoste FkStandard IsValidated and Date
return f doesn't exist on current context on these line.
Could you explain me please.
Select
fk_operateur,Fk_Pst_Std, max(date_formation)
FROM
Formations
GROUP by
Fk_Operateur,Fk_Pst_Std
that's a try in SQL but I'm not able to get others column mentionned before
returns
fk_operateur
FkPstStd
date_formation
1
1
Adate
and many other rows
Since its grouped, to access the mentioned fields, you will have to look in the Values and select the correct item. As in, something like
select new shortFormations
{
FkOperateur = formation.Key.FkOperateur,
FkPstStd = formation.Key.FkPstStd,
IdPoste = formation.FirstOrDefault()
.FkPstStdNavigation.FkPosteNavigation.IdPoste,
....
or order it and then select the correct record
Related
I want to do a LINQ NOT EXISTS on query MULTIPLE TABLES.
All examples on Google or SO are handling two tables I'm working with three so I'm struggling as a newbie on LINQ on how to reference them correctly.
First I tried this LINQ query
var nocertificates = (
from x in rmdb.t_certificates
from ce in rmdb.t_user_certificates
from u in rmdb.t_users
where u.id == ce.uid && ce.value != x.id
select x).AsEnumerable().Select(x => new ViewModelCheckBox()
{
Value = x.id.ToString(),
Name = x.name,
Checked = false
});
I used the ugly three times from as I'm not that good with creating types for joining.
But that gave wrong result and I realized I had to go for a NOT EXISTS
So I built a new query in T-SQL
This is the SQL query it works!
select distinct * from t_certificates tc
where NOT EXISTS
(
select distinct * from t_users tu, t_user_certificates tuc
WHERE tu.email = 'user#email.com'
and tu.id = tuc.[uid]
and tuc.value = tc.id
)
How would I do that in LINQ?
This is the question, I will award my answer for that!
BUT!
When we are at it... I'm really curious on the answer.. Is it possible to do one LINQ query that return an Ienumerable with both those that EXISTS and NOT EXISTS resulting in an object which will hold DIFFERENT VALUES on the checked property EXISTS -> CHECKED = true NOT EXISTS -> CHECKED = false
This is how I create my object.
.Select(x => new ViewModelCheckBox()
{
Value = x.id.ToString(),
Name = x.name,
Checked = this should be different based on exists or not
});
The LINQ answer should look something like this (untested):
var nocertificates =
from x in rmdb.t_certificates
join tuc in (
from u in rmdb.t_users
join ce in rmdb.t_user_certificates on u.id == ce.uid
select ce.value
) on tuc.value = tc.id into tuc
from y in tuc.DefaultIfEmpty()
where y == null
select x;
This is what I ended up using!
var query = (from tc in rmdb.t_certificates
where !(
from tu in rmdb.t_users
from tuc in rmdb.t_user_certificates
where tu.email == username
&& tu.id == tuc.uid
&& tuc.value == tc.id select tc).AsEnumerable().Any()
select new ViewModelCheckBox()
{ Checked = false,
intconverter = tc.id,
Name = tc.name
});
How we can write a LINQ query for following select sql query:
string brandid="1,2,3"
string bodystyleid="1,2,3"
-------------------
-----------------
select * from car
where brandid in (brandid)
and bodystyleid in (brandid)
----------------------
-------------------
My specific requirement is that if brandid or bodystyleid is blank(if user does not select
any checkbox of a particular search option) query should return all record for that particular where condition.
Please guide me.
Thanks,
Paul
In order to fulfil your requirement about returning all items if none are specified, you need to check for the lists being empty.
var brands = brandid.Split(',').Select(x => Int32.Parse(x));
var styles = bodystyleid.Split(',').Select(x => Int32.Parse(x));
var result = from c in car
where (!brands.Any() || brands.Contains(c.brandid))
&& (!styles.Any() || styles.Contains(c.bodystyleid))
select c;
(similar to sgmoore's solution, but includes the check for no brand/style specified)
I've not actually checked how this gets converted back to SQL - it may be more efficient to use a flag to indicate whether there are any values:
var brands = ....; // As above
bool anyBrands = brands.Any()
var result = from c in car
where (!anyBrands || brands.Contains(c.brandid))
.....
Is bodystyleid meant to check brandid or bodystyleid? (I am assuming bodystyleid, however have wrote the query to match the query in the question (brandid))
As a start you could do:
var results = (from c in car
where c.brandid.Contains(brandid)
&& c.bodystyleid.Contains(brandid)
select c).ToList();
var brandids = brandid .Split(',').Select(n => int.Parse(n)).ToList();
var bodyStyleids = bodystyleid.Split(',').Select(n => int.Parse(n)).ToList();
var results =
(from c in car where
brandids.Contains(c.brandid) &&
bodyStyleids.Contains(c.bodystyleid)
select c
).ToList();
the Ids you have are as strings with comma delimiter, you need them to be collections like List of the same type as your Ids of the Car table, so if brandid column is int then brandids has to be List<long>, then you can do
var results = (
from c in cars
where brandids.Contains(c.brandid) && bodystyleid.Contains(c.bodystyleid)
select c).ToList();
I am using BLToolKit in a project of mine and I was trying to get this to work. What I don't like is that I am trying to average a bunch of temps down to the minute, but the select statement that is being generated groups by the minute but then selects the original time. I think I am doing the linq expression correctly (but then again, i am not getting the results i expect). (this is C#, if you care) Anyone know what is going wrong?
var test = (from r in db.SensorReadingRaws
where r.TimeLogged < DateTime.Now.AddMinutes(-2)
group r by new
{
Sensor = r.SensorNumber,
//group time down to the minute
Time = r.TimeLogged.AddSeconds(-1 * r.TimeLogged.Second).AddMilliseconds(-1 * r.TimeLogged.Millisecond)
} into grouped
select new SensorReading
{
SensorNumber = grouped.Key.Sensor,
TimeLogged = grouped.Key.Time,
Reading = (int)grouped.Average(x => x.Reading)
}).ToList();
textBox1.Text = db.LastQuery;
and the resulting query is this
SELECT
[r].[SensorNumber],
[r].[TimeLogged],
Avg([r].[Reading]) as [c1]
FROM
[SensorReadingRaw] [r]
WHERE
[r].[TimeLogged] < #p1
GROUP BY
[r].[SensorNumber],
DateAdd(Millisecond, Convert(Float, -DatePart(Millisecond, [r].[TimeLogged])), DateAdd(Second, Convert(Float, -DatePart(Second, [r].[TimeLogged])), [r].[TimeLogged])),
[r].[TimeLogged]
I discovered that
BLToolkit.Data.Linq.Sql.AsSql<T>(T obj)
can be used as a workaround for this case.
When applying this function to the required grouped key properties in select statement you get rid of grouping/selecting an original field.
It may look something like:
_queryStore.Leads().
GroupBy(x => new {
x.LeadDate.Hour,
x.LeadDate.Minute
}).
Select(x => new {
Hour = Sql.AsSql(x.Key.Hour),
Minute = Sql.AsSql(x.Key.Minute),
Count = x.Count()
});
and in your particular case:
var test = (from r in db.SensorReadingRaws
where r.TimeLogged < DateTime.Now.AddMinutes(-2)
group r by new
{
Sensor = r.SensorNumber,
//group time down to the minute
Time = r.TimeLogged.AddSeconds(-1 * r.TimeLogged.Second).AddMilliseconds(-1 * r.TimeLogged.Millisecond)
} into grouped
select new SensorReading
{
SensorNumber = grouped.Key.Sensor,
TimeLogged = Sql.AsSql(grouped.Key.Time),
Reading = (int)grouped.Average(x => x.Reading)
}).ToList();
I got same issue yesterday.
Today I found a workaround. The idea is to write 2 linq queries. First transforming the data and the second grouping the result:
var bandAndDate =
(from r in repo.Entities
select new {Band = r.Score / 33, r.StartTime.Date});
var examsByBandAndDay =
(from r in bandAndDate
group r by new {r.Band, r.Date } into g
select new { g.Key.Date, g.Key.Band, Count = g.Count() }).ToList();
Both this queries run one SQL that do the job:
SELECT
[t1].[c1] as [c11],
[t1].[c2] as [c21],
Count(*) as [c3]
FROM
(
SELECT
[r].[Score] / 33 as [c2],
Cast(Floor(Cast([r].[StartTime] as Float)) as DateTime) as [c1]
FROM
[Results] [r]
) [t1]
GROUP BY
[t1].[c2],
[t1].[c1]
Given a date, what is the most efficient way to query the last record before that date, any record that equals that date, and the next one after that date.
It should be functionally equivalent to a query like this:
from asset in Assets
where asset.Id == assetId
select new {
Previous = (from a in a.Orders where a.Date < myDate orderby a.Date descending select a).FirstOrDefault(),
Current = (from a in a.Orders where a.Date == myDate select a).SingleOrDefault(),
Next = (from a in a.Orders where a.Date > myDate orderby a.Date select a).FirstOrDefault()
}
As is, this query runs three queries, and presumably has to sort the dataset by myDate three times to do it.
Some similar questions:
How do I get 5 records before AND after a record with a specific ID? (just uses two queries)
How do I get records before and after given one? Not in Linq, and therefore hard for me to take advantage of (my team will get annoyed).
To provide the "most efficient" query depends on what you mean by efficient.
If you want a single query to the database, a single sort of orders by date and finally fast look-ups by date then I suggest the following might be the most efficient. :-)
var orders =
(from a in Assets
where a.Id == assetId
from o in a.Orders
orderby o.Date
select o).ToArray();
var previous = orders.LastOrDefault(o => o.Date < myDate);
var current = orders.SingleOrDefault(o => o.Date == myDate);
var next = orders.FirstOrDefault(o => o.Date > myDate);
This should query the database once for the orders associated with the required asset Id, sort them by date, and return them as an array in memory. Since this is in memory it is now blindingly fast to look for the current, previous & next records for the specified date.
Does your Orders table have a sequential ID field? If so, you might be able to do it with:
from asset in Assets
where asset.Id == assetID
let current = asset.Orders.Where(x => x.Date == myDate).FirstOrDefault()
where current != null
let previous = asset.Orders.Where(x => x.id == current.id - 1).FirstOrDefault()
let next = asset.Orders.Where(x => x.id == current.id + 1).FirstOrDefault()
select new {
Previous = previous,
Current = current,
Next = next
};
If it doesn't, then it'd be a bit more code:
from asset in Assets
where asset.Id == assetID
let current = asset.Orders.Where(x => x.Date == myDate).FirstOrDefault()
where current != null
let previous = asset.Orders.Where(x => x.Date < current.Date).OrderByDescending(x => x.Date).FirstOrDefault()
let next = asset.Orders.Where(x => x.Date > current.Date).OrderBy(x => x.Date).FirstOrDefault()
select new {
Previous = previous,
Current = current,
Next = next
};
That should get compiled into a single SQL query that utilizes sub-queries. IE: the database server will execute multiple queries, but your client program is only submitting one.
Edit One other idea that would work if your Order table had sequential IDs:
var sample = (from asset in Assets
where asset.Id == assetID
let current = asset.Orders.Where(x => x.Date == myDate).FirstOrDefault()
where current != null
from order in asset.Orders
where order.Id == current.id - 1
select order)
.Take(3)
.ToArray();
var Previous = sample[0];
var Current = sample[1];
var Next = sample[2];
Other Answers, for example, SkipWhile etc. very very slow. Good luck ^^
//Current Record
var query
= (from item in db.Employee
where item.UserName.Equals(_username)
select item).SingleOrDefault();
//Next Record
var query
= (from item in db.Employee
where item.UserName.CompareTo(_username) > 0
select item).FirstOrDefault();
//Previous Record
var query
= (from item in db.Employee
where item.UserName.CompareTo(_username) < 0
orderby item.UserName Descending
select item).FirstOrDefault();
Almost the same, but the SQL query plan might be different.
var q =
from asset in Assets
where asset.Id == assetID
select new
{
Previous = asset.Orders.where(a => a.Date == asset.Orders.Where(x => x.Date < myDate).Max(x => x.Date)).FirstOrDefault(),
Current = asset.Orders.Where(x => x.Date == myDate).FirstOrDefault(),
Next = asset.Orders.where(a => a.Date == asset.Orders.Where(x => x.Date > myDate).Min(x => x.Date)).FirstOrDefault()
};
What do I put in my order by?? I want to order by Name. I have moved the orderby after the distinct because I read that it needs to be done last.
var result = (from r in db.RecordDocs
where r.RecordID == recordID
select new
{
DocTypeID = r.Document.DocType.DocTypeID,
Name = r.Document.DocType.Name,
Number = r.Document.DocType.Number
}
).Distinct().OrderBy( );
Just do
.OrderBy(doc => doc.Name)
Another option, if you really prefer the query expression syntax would be to chain your query construction across multiple statements:
var query = from r in db.RecordDocs
where r.RecordID == recordID
select new
{
DocTypeID = r.Document.DocType.DocTypeID,
Name = r.Document.DocType.Name,
Number = r.Document.DocType.Number
};
query = query.Disctinct();
query = from doc in query orderby doc.Name select doc;
Since all of these methods are deferred, this will result in the exact same execution performance.