How can I select data with such linq to sql code, it's something wrong, i must compare WHERE, from st1 and st2, but something wrong. Also spaller didn't light this variables in where
var st1 = (from a in db.RouteDetail
where a.Station == "Гродно"
select new
{
a.Route,
});
var st2 = (from c in db.RouteDetail
where c.Station == "Лида"
select new
{
c.Route,
});
var res = (from d in db.RouteDetail
where st1.Route == st2.Route
select d);
Help me to do this, please.
I think what you mean to do is something like this :
var st1 = (from a in db.RouteDetail
where a.Station == "Гродно"
select new
{
a.Route,
});
var st2 = (from c in db.RouteDetail
where c.Station == "Лида"
select new
{
c.Route,
});
Both st1 and st2 now contain IQueryable types which allow you to enumerate over them. I'm assuming that your two queries only return one result in which case:
var station1 = st1.FirstorDefault();
var station2 = st2.FirstorDefault();
var res = (from d in db.RouteDetail
where station1.Route == station2.Route
select d);
Will do what you need it to do (provided they return a result theres no safety here for null exceptions). If however there is more than one result, it will only return the first match. In which case you will need to work out all the possible compositions from the values in st1 and st2
Related
How can I get the raw SQL generated against the below query in EF 6? I have tried ToString(), ToTraceString() but those are not working and I don't have access to the DbContext object at this point.
IQueryable<AccountApplication> query = AppService.QueryService.GetQueryMatching(spec);
var acccounts = (from a in query
where a.ApplicationId == applicationId && a.Id != 3
select new AccountDto
{
Id = a.Id,
Name = a.Account.AccountName,
ApplicationName = a.Application.ApplicationName,
SubsidaryId = a.Account.SubsidaryId.HasValue ? a.Account.SubsidaryId.Value : 0
}).ToList();
Did you try this
var sql = ((System.Data.Entity.Core.Objects.ObjectQuery)query).ToTraceString();
I'm sorting a large database by the quantity of outgoing relationships. I have a working Cypher query as follows:
optional match (n)-[r]->(m)
return n, Count(r) as c
order by c DESC limit 1;
The Cypher query is working as anticipated. However, as I am debugging and stepping through the Cypher -> Neo4jClient conversion, I cannot seem to find the root of the issue.
public ReturnPayload[] getByConnections()
{
var query = client.Cypher
.OptionalMatch("(p)-[r]->(m)")
.Return((p, r, m, c) => new
{
p = p.As<Person>(),
pid = (int)p.Id(),
e = r.As<RelationshipInstance<Object>>(),
m = m.As<Metadata>(),
c = r.Count()
}).OrderByDescending("c").Limit(1);
var res = query.Results;
var payload = new List<ReturnPayload>();
foreach (var el in res)
{
var t = new ReturnPayload();
t.e = el.e;
t.m = el.m;
t.pid = el.pid;
t.p = el.p;
payload.Add(t);
}
return payload.ToArray<ReturnPayload>();
}
I suspect that a part of the problem may be that I am not utilizing CollectAs<T>() and thus it is referring a count of '1' per each person. Unfortunately, I have attempted using CollectAs<T>() and CollectAsDisctinct<T>() and my resultant JSON architecture is only wrapping each individual element in an array, as opposed to aggregating identical elements into an array proper.
The FOREACH loop is there to assist in converting from the anonymous type into my relatively standard <ReturnPayload> which does not utilize a c object within its parameters.
Your time is appreciated, thank you.
Debugged Query Test:
OPTIONAL MATCH (p)-[r]->(m)
RETURN p AS p, id(p) AS pid, r AS e, m AS m, count(r) AS c
ORDER BY c DESC
LIMIT {p0}
And my 'functional' Cypher query:
optional match (n)-[r]->(m)
return n, Count(r) as c
order by c DESC limit 1;
So, you've identified yourself that you're running two different queries. This is the issue: your C# does not match the Cypher you're expecting.
To make the C# match the working Cypher, change it to this:
var query = client.Cypher
.OptionalMatch("(n)-[r]->(m)")
.Return((n, r) => new
{
n = n.As<Person>(),
c = r.Count()
})
.OrderByDescending("c")
.Limit(1);
That should now produce the same query, and thus the same output as you're expecting from the working Cypher.
On a purely stylistic note, you can also simplify your foreach query to a more functional equivalent:
var payload = query
.Results
.Select(r => new ReturnPayload {
n = r.n,
c = r.c
})
.ToArray();
return payload;
However, as I look closer as your query, it looks like you just want the count for the sake of getting the top 1, then you're throwing it away.
Consider using the WITH clause:
optional match (n)-[r]->(m)
with n as n, count(r) as c
order by c desc
limit 1
return n
You can map that back to C# using similar syntax:
var query = client.Cypher
.OptionalMatch("(n)-[r]->(m)")
.With((n, r) => new
{
n = n.As<Person>(),
c = r.Count()
})
.OrderByDescending("c")
.Limit(1)
.Return(n => new ReturnPayload // <-- Introduce the type here too
{
n = n.As<Person>()
});
Then, you don't need to query for data and just throw it away with another foreach loop. (You'll notice I introduce the DTO type in the Return call as well, so you don't have to translate it out of the anonymous type either.)
(Disclaimer: I'm just typing all of this C# straight into the answer; I haven't double checked the compilation, so my signatures might be slightly off.)
Hope that helps!
I'm currently using Entity Framework for my db access but want to have a look at Dapper. I have classes like this:
public class Course{
public string Title{get;set;}
public IList<Location> Locations {get;set;}
...
}
public class Location{
public string Name {get;set;}
...
}
So one course can be taught at several locations. Entity Framework does the mapping for me so my Course object is populated with a list of locations. How would I go about this with Dapper, is it even possible or do I have to do it in several query steps?
Alternatively, you can use one query with a lookup:
var lookup = new Dictionary<int, Course>();
conn.Query<Course, Location, Course>(#"
SELECT c.*, l.*
FROM Course c
INNER JOIN Location l ON c.LocationId = l.Id
", (c, l) => {
Course course;
if (!lookup.TryGetValue(c.Id, out course))
lookup.Add(c.Id, course = c);
if (course.Locations == null)
course.Locations = new List<Location>();
course.Locations.Add(l); /* Add locations to course */
return course;
}).AsQueryable();
var resultList = lookup.Values;
See here https://www.tritac.com/blog/dappernet-by-example/
Dapper is not a full blown ORM it does not handle magic generation of queries and such.
For your particular example the following would probably work:
Grab the courses:
var courses = cnn.Query<Course>("select * from Courses where Category = 1 Order by CreationDate");
Grab the relevant mapping:
var mappings = cnn.Query<CourseLocation>(
"select * from CourseLocations where CourseId in #Ids",
new {Ids = courses.Select(c => c.Id).Distinct()});
Grab the relevant locations
var locations = cnn.Query<Location>(
"select * from Locations where Id in #Ids",
new {Ids = mappings.Select(m => m.LocationId).Distinct()}
);
Map it all up
Leaving this to the reader, you create a few maps and iterate through your courses populating with the locations.
Caveat the in trick will work if you have less than 2100 lookups (Sql Server), if you have more you probably want to amend the query to select * from CourseLocations where CourseId in (select Id from Courses ... ) if that is the case you may as well yank all the results in one go using QueryMultiple
No need for lookup Dictionary
var coursesWithLocations =
conn.Query<Course, Location, Course>(#"
SELECT c.*, l.*
FROM Course c
INNER JOIN Location l ON c.LocationId = l.Id
", (course, location) => {
course.Locations = course.Locations ?? new List<Location>();
course.Locations.Add(location);
return course;
}).AsQueryable();
I know I'm really late to this, but there is another option. You can use QueryMultiple here. Something like this:
var results = cnn.QueryMultiple(#"
SELECT *
FROM Courses
WHERE Category = 1
ORDER BY CreationDate
;
SELECT A.*
,B.CourseId
FROM Locations A
INNER JOIN CourseLocations B
ON A.LocationId = B.LocationId
INNER JOIN Course C
ON B.CourseId = B.CourseId
AND C.Category = 1
");
var courses = results.Read<Course>();
var locations = results.Read<Location>(); //(Location will have that extra CourseId on it for the next part)
foreach (var course in courses) {
course.Locations = locations.Where(a => a.CourseId == course.CourseId).ToList();
}
Sorry to be late to the party (like always). For me, it's easier to use a Dictionary, like Jeroen K did, in terms of performance and readability. Also, to avoid header multiplication across locations, I use Distinct() to remove potential dups:
string query = #"SELECT c.*, l.*
FROM Course c
INNER JOIN Location l ON c.LocationId = l.Id";
using (SqlConnection conn = DB.getConnection())
{
conn.Open();
var courseDictionary = new Dictionary<Guid, Course>();
var list = conn.Query<Course, Location, Course>(
query,
(course, location) =>
{
if (!courseDictionary.TryGetValue(course.Id, out Course courseEntry))
{
courseEntry = course;
courseEntry.Locations = courseEntry.Locations ?? new List<Location>();
courseDictionary.Add(courseEntry.Id, courseEntry);
}
courseEntry.Locations.Add(location);
return courseEntry;
},
splitOn: "Id")
.Distinct()
.ToList();
return list;
}
Something is missing. If you do not specify each field from Locations in the SQL query, the object Location cannot be filled. Take a look:
var lookup = new Dictionary<int, Course>()
conn.Query<Course, Location, Course>(#"
SELECT c.*, l.Name, l.otherField, l.secondField
FROM Course c
INNER JOIN Location l ON c.LocationId = l.Id
", (c, l) => {
Course course;
if (!lookup.TryGetValue(c.Id, out course)) {
lookup.Add(c.Id, course = c);
}
if (course.Locations == null)
course.Locations = new List<Location>();
course.Locations.Add(a);
return course;
},
).AsQueryable();
var resultList = lookup.Values;
Using l.* in the query, I had the list of locations but without data.
Not sure if anybody needs it, but I have dynamic version of it without Model for quick & flexible coding.
var lookup = new Dictionary<int, dynamic>();
conn.Query<dynamic, dynamic, dynamic>(#"
SELECT A.*, B.*
FROM Client A
INNER JOIN Instance B ON A.ClientID = B.ClientID
", (A, B) => {
// If dict has no key, allocate new obj
// with another level of array
if (!lookup.ContainsKey(A.ClientID)) {
lookup[A.ClientID] = new {
ClientID = A.ClientID,
ClientName = A.Name,
Instances = new List<dynamic>()
};
}
// Add each instance
lookup[A.ClientID].Instances.Add(new {
InstanceName = B.Name,
BaseURL = B.BaseURL,
WebAppPath = B.WebAppPath
});
return lookup[A.ClientID];
}, splitOn: "ClientID,InstanceID").AsQueryable();
var resultList = lookup.Values;
return resultList;
There is another approach using the JSON result. Even though the accepted answer and others are well explained, I just thought about an another approach to get the result.
Create a stored procedure or a select qry to return the result in json format. then Deserialize the the result object to required class format. please go through the sample code.
using (var db = connection.OpenConnection())
{
var results = await db.QueryAsync("your_sp_name",..);
var result = results.FirstOrDefault();
string Json = result?.your_result_json_row;
if (!string.IsNullOrEmpty(Json))
{
List<Course> Courses= JsonConvert.DeserializeObject<List<Course>>(Json);
}
//map to your custom class and dto then return the result
}
This is an another thought process. Please review the same.
I'm trying to get a paged query to work properly using LINQ and NHibernate. On a single table, this works perfect, but when more than one table is joined, it's causing me havoc. Here is what I have so far.
public virtual PagedList<Provider> GetPagedProviders(int startIndex, int count, System.Linq.Expressions.Expression<Func<Record, bool>> predicate) {
var firstResult = startIndex == 1 ? 0 : (startIndex - 1) * count;
var query = (from p in session.Query<Record>()
.Where(predicate)
select p.Provider);
var rowCount = query.Select(x => x.Id).Distinct().Count();
var pageOfItems = query.Distinct().Skip(firstResult).Take(count).ToList<Provider>();
return new PagedList<Provider>(pageOfItems, startIndex, count, rowCount);
}
There are a couple issues I'm having with this. First off, the rowCount variable is pulling back a COUNT(*) on a join that has one to many. So my count is way off of what is should be, I'm expecting 129, but getting back over 1K.
The second issue I'm happening is with the results. If I'm on the first page (firstResult = 0), then I'm getting correct results. However, if firstResult is something other than 0, it produces completely different SQL. Below is the SQL generated by both scenarios, I've trimmed out some of the fat to make it a little more readable.
--firstResult = 0
select distinct TOP (30) provider1_.Id as Id12_, provider1_.TaxID as TaxID12_,
provider1_.Facility_Name as Facility5_12_, provider1_.Last_name as Last6_12_,
provider1_.First_name as First7_12_, provider1_.MI as MI12_
from PPORecords record0_ left outer join PPOProviders provider1_ on record0_.Provider_id=provider1_.Id,
PPOProviders provider2_ where record0_.Provider_id=provider2_.Id
and provider2_.TaxID='000000000'
--firstResult = 30
SELECT TOP (30) Id12_, TaxID12_, Facility5_12_, Last6_12_, First7_12_, MI12_,
FROM (select distinct provider1_.Id as Id12_, provider1_.TaxID as TaxID12_,
provider1_.Facility_Name as Facility5_12_,
provider1_.Last_name as Last6_12_,
provider1_.First_name as First7_12_,
provider1_.MI as MI12_,
ROW_NUMBER() OVER(ORDER BY CURRENT_TIMESTAMP) as __hibernate_sort_row
from PPORecords record0_ left outer join PPOProviders provider1_ on record0_.Provider_id=provider1_.Id,
PPOProviders provider2_
where record0_.Provider_id=provider2_.Id and provider2_.TaxID='000000000') as query
WHERE query.__hibernate_sort_row > 30
ORDER BY query.__hibernate_sort_row
The problem with the second query is the "distinct" keyword is not present on the outer query, only the inner query. Any ideas how to correct this?
Thanks for any suggestions!
[UPDATE]
This is the code that is building the the Linq query predicate.
private Expression<Func<Record, bool>> ParseQueryExpression(string Query) {
Expression<Func<Record, bool>> mExpression = x => true;
string[] splitQuery = Query.Split('|');
foreach (string query in splitQuery) {
if (string.IsNullOrEmpty(query))
continue;
int valStartIndex = query.IndexOf('(');
string variable = query.Substring(0, valStartIndex);
string value = query.Substring(valStartIndex + 1, query.IndexOf(')') - valStartIndex - 1);
switch (variable) {
case "tax":
mExpression = x => x.Provider.TaxID == value;
break;
case "net":
mExpression = Combine<Record>(mExpression, x => x.Network.Id == int.Parse(value));
break;
case "con":
mExpression = Combine<Record>(mExpression, x => x.Contract.Id == int.Parse(value));
break;
case "eff":
mExpression = Combine<Record>(mExpression, x => x.Effective_Date >= DateTime.Parse(value));
break;
case "trm":
mExpression = Combine<Record>(mExpression, x => x.Term_Date <= DateTime.Parse(value));
break;
case "pid":
mExpression = Combine<Record>(mExpression, x => x.Provider.Id == long.Parse(value));
break;
case "rid":
mExpression = Combine<Record>(mExpression, x => x.Rate.Id == int.Parse(value));
break;
}
}
return mExpression;
}
It seems as if the Linq provider has some "unexpected" behaviour there. I could reproduce the issue with the rowCount that you are describing and also encountered some issues when trying to fix it with a subquery.
If I understand your intentions correctly you basically want to have a paged list of Providers whose Records match certain criteria.
In that case I would suggest using a subquery. However, I tried implementing the subquery with the Query() method but it did not work. So I tried the QueryOver() method which worked flawlessly. In your case the desired queries would look like this:
Provider pAlias = null;
var query = session.QueryOver<Provider>(() => pAlias).WithSubquery
.WhereExists(QueryOver.Of<Record>()
.Where(predicate)
.And(r => r.Provider.Id == pAlias.Id)
.Select(r => r.Provider));
var rowCount = query.RowCount();
var pageOfItems = query.Skip(firstResult).Take(count).List<Provider>();
That way you do not have to struggle with the Distinct(). And as much as I personally like and use NHibernate.Linq, I suppose, if it does not work in a given situation, one should use something else that works.
Edit: Splitting the query into smaller units.
// the method ParseQueryExpression() does not need to be modified, the Expression should work like that
System.Linq.Expressions.Expression<Func<Record, bool>> predicate = x => x.Provider.TaxID == "000000000";
// Query to evaluate predicate
IQueryable<Record> queryId = session.Query<Record>().Where(predicate).Select(r => r.Provider);
// extracting the IDs to use in a subquery
List<int> idList = queryId.Select(p => p.Id).Distinct().ToList();
// total count of distinct Providers
int rowCount = idList.Count;
// new Query on Provider, using the distinct Ids
var query = session.Query<Provider>().Where(p => idList.Contains(p.Id));
// the List<Provider> to display on the page
var pageOfItems = query.Skip(firstResult).Take(count).ToList();
The problem here is that you have multiple queries and therefore multiple roundtrips to the db. Another problem apperas when you examine the generated sql. The subquery idList.Contains(p.Id) will generate an in-clause with a lot of parameters.
As you can see, these are NHibernate.Linq queries. That is because the new QueryOver feature is not a true Linq provider and does not work well with dynamic Linq expressions.
You could get around that limitation by using Detached QueryOvers. The drawback here is that you would have to modify your ParseQueryExpression() somehow, e.g. like that:
private QueryOver<Record> ParseQueryExpression(string Query)
{
Record rAlias = null;
var detachedQueryOver = QueryOver.Of<Record>(() => rAlias)
.JoinQueryOver(r => r.Provider)
.Where(() => rAlias.Provider.TaxID == "000000000")
.Select(x => x.Id);
// modify your method to match the return value
return detachedQueryOver;
}
// in your main method
var detachedQueryOver = QueryOver.Of<Record>()
.WithSubquery
.WhereProperty(r => r.Id
.In(this.ParseQueryExpression(...));
var queryOverList = session.QueryOver<Provider>()
.WithSubquery
.WhereProperty(x => x.Id)
.In(detachedQueryOver.Select(r => r.Provider.Id));
int rowCount = queryOverList.RowCount();
var pageOfItems = queryOverList.Skip(firstResult).Take(count).List();
Well, I hope you are not too confused by that.
Is there a online system which converts SQL - LINQ or can anyone else help convert the SQL - LINQ below?
SELECT MIN(startTime) As startTime, MAX(endTime) As endTime
FROM tblRA
LEFT JOIN tblA ON tblRA.asID = tblA.asID
WHERE 'xxxxxx' BETWEEN tblRA.startDate AND tblRA.endDate
AND tblA.availabilityDayOfWeek = 7
The main area I am having trouble is the .MAX/.MIN.
Heres what I have so far
public List<string> GetResourceAvailabilitiesByDate(DateTime searchDate)
{
DayOfWeek dayOfWeek = searchDate.DayOfWeek;
var minVal = from a in dc.tblResourceAvailabilities
join b in dc.tblAvailabilities on a.asID equals b.asID
where searchDate.Date >= a.startDate.Date && searchDate.Date <= a.endDate.Value.Date
&& b.availabilityDayOfWeek == (int)dayOfWeek
select b.startTime.ToShortTimeString();;
var maxVal = from a in dc.tblResourceAvailabilities
join b in dc.tblAvailabilities on a.asID equals b.asID
where searchDate.Date >= a.startDate.Date && searchDate.Date <= a.endDate.Value.Date
&& b.availabilityDayOfWeek == (int)dayOfWeek
select b.endTime.ToShortTimeString();
var min = minVal.Min(minVal.Min);
var max = maxVal.Max();
return min,max;
Thanks in advance for any help
Clare
I think your code is a little bit incorrect, and the first symptom of it is that you are using repeated code to define minval and maxval. I tried to simulate something similar to what you want and came to the following code, please adapt it to your needs.
public List<string> GetResourceAvailabilitiesByDate(DateTime searchDate)
{
DayOfWeek dayOfWeek = searchDate.DayOfWeek;
var vals = from a in dc.tblResourceAvailabilities
join b in dc.tblAvailabilities on a.asID equals b.asID
where searchDate.Date >= a.startDate.Date && searchDate.Date <= a.endDate.Value.Date
&& b.availabilityDayOfWeek == (int)dayOfWeek
select b;
var min = vals.Min(v => v.startTime).ToShortTimeString();
var max = vals.Max(v => v.startTime).ToShortTimeString();
return new List<string>() { min, max };
}
Some comments on your code, assuming it's C#.
You are trying to return an array of strings when you should be returning an array of dates.
Your where clause is pretty confuse. You're comparing the search date with startdate.Date and endDate.Value.Date. It does not make much sense.
Your select clause could select only b, or a, or whatever. You don't really need to select the date in it.