I want to get column values with group by. My tables are like this:
Table1
Id
Material
Length
Table2
Id
Name
Type
....
..
.
I can get plain sql query in a function.
public GetValues(tableName, columnName){
string sql = "select " + columnName + " from " + tableName + " group by " + columnName;
}
Is possible doing this via Entity Framework?
Create your table in EF with code first. A simple lambda group by looks like:
List<MyRecord> myTable = new List<UserQuery.MyRecord>();
var items = myTable.GroupBy(t => t.MyColumn);
public class MyRecord
{
public int MyRecordID { get; set; }
public string MyColumn { get; set;}
}
The EF equivalent is, using the entity you created would be:
MyEntities dbContext = new MyEntities()
using dbContext
{
var items = dbContext.MyTable // .. then a suitable lambda expression
}
Related
Sorry for my bad English
Note: Npgsql does not supporting json query with EF Core Mapping directly
As yo know PostgreSQL is supporting json and hybrid data. And if you want to query, you can use syntax like this
select *
from archive.ArchiveObject
where FileInfo->>'FileName' = 'name.ext';
For my question here is sample table and sample class
Table:
CREATE TABLE archive."ArchiveObject"
(
"Id" bigint NOT NULL DEFAULT nextval('archive."ArchiveObject_Id_seq"'::regclass),
"Uid" uuid NOT NULL,
...
...
...
"FileInfo" json,
...
...
)
and here is C# classes for this table
[Table("ArchiveObject", Schema = CX.Schema)]
public partial class ArchiveObject
{
[Key]
public long Id { get; set; }
[Required]
public Guid Uid { get; set; }
[Column("FileInfo", TypeName = "json")]
public string _FileInfo { get; set; }
[NotMapped]
public ObjectFileInfo FileInfo
{
//get;set;
get
{
return string.IsNullOrEmpty(_FileInfo) ? null : JsonConvert.DeserializeObject<ObjectFileInfo>(_FileInfo);
}
set
{
_FileInfo = value != null ? JsonConvert.SerializeObject(value) : null;
}
}
...
...
}
OK. When I used linq or lambda like this no problem
var query = from x in db.ArchiveObject
where x.Id < 65535
select x;
generates
"SELECT x."Id", x."CreatedAt", x."KellePaca", x."Tags", x."Uid", x."UpdateHistory", x."VirtualPathId", x."FileInfo"
FROM archive."ArchiveObject" AS x
WHERE (x."Id" < 65535)
but I can't query json area named FileInfo field like this.
select *
from archive.ArchiveObject
where FileInfo->>'FileName' = 'name.ext' ;
because of EF doesn't have any Provider for convert to sql "file_info->>'FileName'"
I'm searched and found this terms
ExpressionVisitor, QueryProvider, BinaryExpression,
ParameterExpression, ObjectQuery.ToTraceString, Expression
and also found this documents and answers
How to convert an expression tree to a partial SQL query?
https://www.codeproject.com/Articles/22819/How-To-LINQ-To-SQL-Part-III
I'm believe can be generate [ file_info->>'FileName' = 'name.ext' ; ] query using this documents. But I can't get it.
public static IQueryable<ArchiveObject> FileNameEquals(this IQueryable<ArchiveObject> source, string s)
{
....
}
or what?
Please can you show me simple example.
Background
I'm attempting to use ServiceStack.OrmLite to grab some values (so I can cache them to run some processing against them).
I need to grab a combination of three values, and I have a custom SQL statement that will yield them (does the joins, etc.)
Because this will be a large list of combinations, I'd like to pass in some lists of values and use Sql.In to filter to only the results that have those values.
Specifics
I need to check whether an invoice is unique to a firm and another value (called ClaimLawsuitID here).
so have my poco:
public class FirmIDClaimLawsuitIDInvoiceNumberCombination
{
public string FirmID { get; set; }
public string ClaimLawsuitID { get; set; }
public string InvoiceNumber { get; set; }
}
and I have my SQL statement:
select tblDefenseInvoice.FirmID, tblDefInvClaimantDetail.ClaimLawsuitID, tblDefInvClaimantDetail.invoiceNumber
from tblDefenseInvoice
inner join tblDefInvClaimantDetail
on(tblDefenseInvoice.DefenseInvoiceID = tblDefInvClaimantDetail.DefenseInvoiceID)
I would like to run the following:
public List<FirmIDClaimLawsuitIDInvoiceNumberCombination> GetFirmIDClaimLawsuitIDInvoiceNumberCombinationsForExistingItems(IEnumerable<int> firmIds, IEnumerable<long> claimLawsuitIDs, IEnumerable<string> invoiceNumbers)
{
var sql = #"select tblDefenseInvoice.FirmID, tblDefInvClaimantDetail.ClaimLawsuitID, tblDefInvClaimantDetail.invoiceNumber
from tblDefenseInvoice
inner join tblDefInvClaimantDetail
on(tblDefenseInvoice.DefenseInvoiceID = tblDefInvClaimantDetail.DefenseInvoiceID)";
var ev = OrmLiteConfig.DialectProvider.ExpressionVisitor<tblClaimLawsuit>();
var firmFilter = PredicateBuilder.True<tblDefenseInvoice>();
var claimLawsuitFilter = PredicateBuilder.True<tblDefInvClaimantDetail>();
var invoiceNumberFilter = PredicateBuilder.True<tblDefInvClaimantDetail>();
firmFilter = x => Sql.In(x.FirmID, firmIds);
claimLawsuitFilter = x => Sql.In(x.ClaimLawsuitID, claimLawsuitIDs);
invoiceNumberFilter = x => Sql.In(x.InvoiceNumber, invoiceNumbers);
ev.Select(sql);
ev.Where(firmFilter);
ev.Where(claimLawsuitFilter);
ev.Where(invoiceNumberFilter);
return dal.DB.Select<FirmIDClaimLawsuitIDInvoiceNumberCombination>(ev.ToSelectStatement());
}
Question
Is this possible to achieve this way?
Is there some other way of achieving this within ServiceStack's OrmLite that is cleaner and I'm unaware of?
Since I was selecting to a POCO, I simply needed to add the filters based on that POCO.
The following worked just fine:
public List<FirmIDClaimLawsuitIDInvoiceNumberCombination>
GetFirmIDClaimLawsuitIDInvoiceNumberCombinationsForExistingItems(
IEnumerable<long> firmIds,
IEnumerable<long> claimLawsuitIDs)
{
var sql = #"select tblDefenseInvoice.FirmID, tblDefInvClaimantDetail.ClaimLawsuitID, tblDefInvClaimantDetail.invoiceNumber
from tblDefenseInvoice
inner join tblDefInvClaimantDetail
on(tblDefenseInvoice.DefenseInvoiceID = tblDefInvClaimantDetail.DefenseInvoiceID)";
var ev = OrmLiteConfig.DialectProvider.ExpressionVisitor<FirmIDClaimLawsuitIDInvoiceNumberCombination>();
var firmFilter = PredicateBuilder.True<FirmIDClaimLawsuitIDInvoiceNumberCombination>();
var claimLawsuitFilter = PredicateBuilder.True<FirmIDClaimLawsuitIDInvoiceNumberCombination>();
firmFilter = x => Sql.In(x.FirmID, firmIds);
claimLawsuitFilter = x => Sql.In(x.ClaimLawsuitID, claimLawsuitIDs);
ev.Select(sql);
ev.Where(firmFilter);
ev.Where(claimLawsuitFilter);
return dal.DB.Select<FirmIDClaimLawsuitIDInvoiceNumberCombination>(ev.ToSelectStatement());
}
If I want single primitive value like int, string, float etc I can do like this.
using (var db = new SQLiteConnection(DbPath))
{
double i = db.CreateCommand("select salary from PersonMaster where personId = ?", 9).ExecuteScalar<double>();
}
If I try to return whole object of person master i.e. single row the below code returns null
using (var db = new SQLiteConnection(DbPath))
{
PersonMaster objPersonMaster = db.CreateCommand("select * from PersonMaster where personId = ?", 9).ExecuteScalar<PersonMaster>();
}
I compulsory have to use this
using (var db = new SQLiteConnection(DbPath))
{
List<PersonMaster> lstPersonMaster = db.Query<PersonMaster>("select * from PersonMaster where personId = ?", 9);
PersonMaster objPersonMaster = lstPersonMaster.First();
}
Is there any way to get single row as object, rather than dealing with List<T>
I am assuming you are using SQLite-Net. If that is the case you can use the Find method. Find gets an object using its primary key.
The personId field needs the PrimaryKey attribute as follows:
public class PersonMaster
{
[PrimaryKey]
public int personId { get; set; }
public string name { get; set; }
public decimal salary { get; set; }
}
Then you can use Find like so:
// get person 9
PersonMaster person9 = db.Find<PersonMaster>(9);
You can either use "TOP(1) yourquery" or "yourquery LIMIT 1"
if you just want to get rid of the list step, you can do it directly:
PersonMaster objPersonMaster = db.Query<PersonMaster>("select * from PersonMaster where personId = ?", 9).First();
Of course you have to deal with a possible exception in case nothing is returned, but you should do this also with the list approach anyway.
It looks like NH gets MAX(ID) only once, at first insert and then stores this value internally, this causes me some problems when other processes inserts data. Then I have not actual ID and duplicate key exception is thrown.
Lets imagine we have table Cats
CREATE TABLE Cats(ID int, Name varchar(25))
Then we have corresponding mapping done with FluentNhibernate
public class CatMap : ClassMap<Cat>
{
public CatMap()
{
Id(m=>m.ID).GeneratedBy.Increment();
Map(m=>.Name);
}
}
All I want to achieve is to insert my Cat records with ID's generated by NHibernate using SELECT MAX(ID) FROM Cats before any insert. Executing Session.Flush after any commit dosnt work. I'v done some investigation using SQL Server profiler, and this sql stetement is executed only once (at first insert) - other inserts doesnt force to retreive actual MAX(ID). I know that other algorithms like HiLo are better, but I cant replace it.
As you found out, the NHibernate Increment id generator was not intended for use in a multi-user environment. You state that using a HiLo generator is not an option so you're left with these options:
use the Native generator and change the id column to use the database supported identity mechanism
use the Assigned generator and write code to determine the next valid id
create a Custom generator where you implement the IIdentifierGenerator interface to do what you need
Below is sample code for a custom generator that uses a generalized proc to get an ID for a given table. The main issue with this approach is that you must wrap the code in something like a Unit of Work pattern to ensure the 'select max(id) ..." and the insert are covered by the same database transaction. The IIdentifierGenerator link has the XML mapping you need to wire up this custom generator.
using System;
using System.Collections.Generic;
using System.Data;
using NHibernate.Dialect;
using NHibernate.Engine;
using NHibernate.Id;
using NHibernate.Persister.Entity;
using NHibernate.Type;
namespace YourCompany.Stuff
{
public class IdGenerator : IIdentifierGenerator, IConfigurable
{
private string _tableName;
// The "select max(id) ..." query will go into this proc:
private const string DefaultProcedureName = "dbo.getId";
public string ProcedureName { get; protected set; }
public string TableNameParameter { get; protected set; }
public string OutputParameter { get; protected set; }
public IdGenerator()
{
ProcedureName = DefaultProcedureName;
TableNameParameter = "#tableName";
OutputParameter = "#newID";
}
public object Generate(ISessionImplementor session, object obj)
{
int newId;
using (var command = session.Connection.CreateCommand())
{
var tableName = GetTableName(session, obj.GetType());
command.CommandType = CommandType.StoredProcedure;
command.CommandText = ProcedureName;
// Set input parameters
var parm = command.CreateParameter();
parm.Value = tableName;
parm.ParameterName = TableNameParameter;
parm.DbType = DbType.String;
command.Parameters.Add(parm);
// Set output parameter
var outputParameter = command.CreateParameter();
outputParameter.Direction = ParameterDirection.Output;
outputParameter.ParameterName = OutputParameter;
outputParameter.DbType = DbType.Int32;
command.Parameters.Add(outputParameter);
// Execute the stored procedure
command.ExecuteNonQuery();
var id = (IDbDataParameter)command.Parameters[OutputParameter];
newId = int.Parse(id.Value.ToString());
if (newId < 1)
throw new InvalidOperationException(
string.Format("Could not retrieve a new ID with proc {0} for table {1}",
ProcedureName,
tableName));
}
return newId;
}
public void Configure(IType type, IDictionary<string, string> parms, Dialect dialect)
{
_tableName = parms["TableName"];
}
private string GetTableName(ISessionImplementor session, Type objectType)
{
if (string.IsNullOrEmpty(_tableName))
{
//Not set by configuration, default to the mapped table of the actual type from runtime object:
var persister = (IJoinable)session.Factory.GetClassMetadata(objectType);
var qualifiedTableName = persister.TableName.Split('.');
_tableName = qualifiedTableName[qualifiedTableName.GetUpperBound(0)]; //Get last string
}
return _tableName;
}
}
}
given a query in the form of an ICriteria object, I would like to use NHibernate (by means of a projection?) to find an element's order,
in a manner equivalent to using
SELECT ROW_NUMBER() OVER (...)
to find a specific item's index in the query.
(I need this for a "jump to page" functionality in paging)
any suggestions?
NOTE: I don't want to go to a page given it's number yet - I know how to do that - I want to get the item's INDEX so I can divide it by page size and get the page index.
After looking at the sources for NHibernate, I'm fairly sure that there exists no such functionality.
I wouldn't mind, however, for someone to prove me wrong.
In my specific setting, I did solve this problem by writing a method that takes a couple of lambdas (representing the key column, and an optional column to filter by - all properties of a specific domain entity). This method then builds the sql and calls session.CreateSQLQuery(...).UniqueResult(); I'm not claiming that this is a general purpose solution.
To avoid the use of magic strings, I borrowed a copy of PropertyHelper<T> from this answer.
Here's the code:
public abstract class RepositoryBase<T> where T : DomainEntityBase
{
public long GetIndexOf<TUnique, TWhere>(T entity, Expression<Func<T, TUnique>> uniqueSelector, Expression<Func<T, TWhere>> whereSelector, TWhere whereValue) where TWhere : DomainEntityBase
{
if (entity == null || entity.Id == Guid.Empty)
{
return -1;
}
var entityType = typeof(T).Name;
var keyField = PropertyHelper<T>.GetProperty(uniqueSelector).Name;
var keyValue = uniqueSelector.Compile()(entity);
var innerWhere = string.Empty;
if (whereSelector != null)
{
// Builds a column name that adheres to our naming conventions!
var filterField = PropertyHelper<T>.GetProperty(whereSelector).Name + "Id";
if (whereValue == null)
{
innerWhere = string.Format(" where [{0}] is null", filterField);
}
else
{
innerWhere = string.Format(" where [{0}] = :filterValue", filterField);
}
}
var innerQuery = string.Format("(select [{0}], row_number() over (order by {0}) as RowNum from [{1}]{2}) X", keyField, entityType, innerWhere);
var outerQuery = string.Format("select RowNum from {0} where {1} = :keyValue", innerQuery, keyField);
var query = _session
.CreateSQLQuery(outerQuery)
.SetParameter("keyValue", keyValue);
if (whereValue != null)
{
query = query.SetParameter("filterValue", whereValue.Id);
}
var sqlRowNumber = query.UniqueResult<long>();
// The row_number() function is one-based. Our index should be zero-based.
sqlRowNumber -= 1;
return sqlRowNumber;
}
public long GetIndexOf<TUnique>(T entity, Expression<Func<T, TUnique>> uniqueSelector)
{
return GetIndexOf(entity, uniqueSelector, null, (DomainEntityBase)null);
}
public long GetIndexOf<TUnique, TWhere>(T entity, Expression<Func<T, TUnique>> uniqueSelector, Expression<Func<T, TWhere>> whereSelector) where TWhere : DomainEntityBase
{
return GetIndexOf(entity, uniqueSelector, whereSelector, whereSelector.Compile()(entity));
}
}
public abstract class DomainEntityBase
{
public virtual Guid Id { get; protected set; }
}
And you use it like so:
...
public class Book : DomainEntityBase
{
public virtual string Title { get; set; }
public virtual Category Category { get; set; }
...
}
public class Category : DomainEntityBase { ... }
public class BookRepository : RepositoryBase<Book> { ... }
...
var repository = new BookRepository();
var book = ... a persisted book ...
// Get the index of the book, sorted by title.
var index = repository.GetIndexOf(book, b => b.Title);
// Get the index of the book, sorted by title and filtered by that book's category.
var indexInCategory = repository.GetIndexOf(book, b => b.Title, b => b.Category);
As I said, this works for me. I'll definitely tweak it as I move forward. YMMV.
Now, if the OP has solved this himself, then I would love to see his solution! :-)
ICriteria has this 2 functions:
SetFirstResult()
and
SetMaxResults()
which transform your SQL statement into using ROW_NUMBER (in sql server) or limit in MySql.
So if you want 25 records on the third page you could use:
.SetFirstResult(2*25)
.SetMaxResults(25)
After trying to find an NHibernate based solution for this myself, I ultimately just added a column to the view I happened to be using:
CREATE VIEW vw_paged AS
SELECT ROW_NUMBER() OVER (ORDER BY Id) AS [Row], p.column1, p.column2
FROM paged_table p
This doesn't really help if you need complex sorting options, but it does work for simple cases.
A Criteria query, of course, would look something like this:
public static IList<Paged> GetRange(string search, int rows)
{
var match = DbSession.Current.CreateCriteria<Job>()
.Add(Restrictions.Like("Id", search + '%'))
.AddOrder(Order.Asc("Id"))
.SetMaxResults(1)
.UniqueResult<Paged>();
if (match == null)
return new List<Paged>();
if (rows == 1)
return new List<Paged> {match};
return DbSession.Current.CreateCriteria<Paged>()
.Add(Restrictions.Like("Id", search + '%'))
.Add(Restrictions.Ge("Row", match.Row))
.AddOrder(Order.Asc("Id"))
.SetMaxResults(rows)
.List<Paged>();
}