Nhibernate also offers an objectoriented query by criteria api that can be. It is typesafe with a familiar syntax to lambda expressions and linq. To perform a distinct query you can set the projection on the criteria to projections. Im in the process of transitioning from criteria api to linq to nhibernate, and this little method has been very helpful. Select distinct with nhibernate 29032011 by ajerrison leave a comment i found a blog post on stackoverflow about how to do the equivalent of sqls select distinct in nhibernate, but i cant seem to find it again so here is what i got from it. Loading readonly entities from an hql querycriteria. Ayende has discussed these in detail with the criteria api, but i dont think a blog series on queryover is really complete without mentioning them again.
The problems that exists in the sql world still apply, and it can only be used in hql, not it criteria api. Get distinct result set from nhibernate using criteria api. If your linq construct contains anything that cannot be interpreted by the database e. The power of the criteria api is such that you can create dynamic queries with ease which would be a hassle if we were to use pure hql which would require substantial string concatenations in. Net method of your own then linq achieves the desired result by doing as much of the query as it can in the db and then the rest of the work is applied to an in memory collection. The other thing we need to do is to provide it a list of models that we will map. I have recently created a method to apply select distinct based on a mapped object type. I use the following extension method to page my criteria queries. Criteria, queryover, linq to nhibernate, hql e sql. Creating nhibernate linq query from criteria chad lee. Following is the simplest example of a criteria query is one, which will simply return every object that corresponds to the. Here are the examples of the csharp api class nhibernate.
The criteria api for nhibernate gives us a really easy way to perform paged queries. The hibernate forum is a neverending source of inspiration when it comes to solving reallife problems you might bump into when developing an enterprise application. Nhibernate automatically maps objects to the database so. Hi all, im using the queryover api that is part of nhibernate 3. Select all download jpa criteria apidistinctexample. Nhibernate contains the most recent log4net binary, or you can download the entire log4net install package. This tutorial provide step by step instructions on using hibernate 3. Linq features are contained in nhibernate self in the version but i am missing the described feature, which i really like. Oct 04, 2014 distinct, order by and hibernate hql posted on october 4, 2014 by hedleyproctor recently someone posted a question on stackoverflow explaining that they were having a problem with a hibernate hql query that involved both order by and a distinct in the select. The nhibernate query by criteria api lets you build a query by manipulating criteria objects at runtime.
I would like to get a row count, but the method im using returns all objects. This doesnt happen with linq, it always performs a distinct root entity selection, but it also happens with criteria and queryover. Apr 03, 2009 the criteria api for nhibernate gives us a really easy way to perform paged queries. Distinct, order by and hibernate hql posted on october 4, 2014 by hedleyproctor recently someone posted a question on stackoverflow explaining that they were having a problem with a hibernate hql query that involved both order by and a distinct in the select. Hibernate uses a powerful query language hql that is similar in appearance to sql. Always easier when you can take a peek under the hood. I am new in nhibernate and i want to convert following sql query in nhibernate criteria select distinct freportid, ffiscalyear from tfcmaster where fpropertyid100 i tried this.
Hibernate group by using criteria query how to program with. A while ago i added mutli query to nhibernate, but i didnt have the time to add multi criteria capabilties in time for the 1. This post covers a nice range of realworld usage examples. Its actively developed, fully featured and used in thousands of successful projects.
As it turn out, i managed to implement it about three weeks ago, and only now i had enough time to sit and document it. Browse other questions tagged distinct criteriaapi hibernatecriteria nhibernatecriteria detachedcriteria or ask your own question. Hibernate distinct query returning two columns result. By voting up you can indicate which examples are most useful and appropriate. Needs work for production, but method is working great in dev, only used it for one entity so far. Nhibernate is a mature, open source objectrelational mapper for the. Nhibernate and fluentnhibernate are already in the project but you can find these files on nuget. Microsoft provides a free version of visual studio, which also contains sql server and it can be downloaded from following are the steps for the installation step 1. Need the ability to specify that results of a criteria query should be distinct, especially when joining to a collection. So the criteria equivalent of the hql statement select distinct parent from parent as parent join parent. Projection of distinct value types and export to a dto class database level, give it an alias and sort by the alias. You then include the columns that you wish to return. Now, nhibernates criteria api is pretty powerful, but the learning curve is indeed.
I need to write a query that returns all the distinct orders that match criteria b, where b could be anything from the date time created, to the order amount to the sku on the orderitem and i need to be able to order the results by any of the columns on the order class. It applies this to an iqueryover object property of class. The result is then turned back into an stronglytyped object by setting the result transformer to aliastobeanresulttransformer passing in the type that the result should be transformed into. Jun 28, 2014 otherwise, nhibernate will throw an exception telling you that the query did not return a unique result. With this native query using isqlquery and the statement distinct is necessary because the. How do i get row count using the nhibernate queryover api. Nov 02, 2010 i wrote in current project typical funcion to count the number of elements in db for specific criteria using nhibernate hql. You can still use hibernate tools with hibernate orm 4 libraries to generate the mappingsschemas that will work with hibernate orm 5. Nhibernate criteria api group by example non persisted class. So ive ended up with a hibernate hql query that looks. Nhibernate automatically maps objects to the database so you can concentrate on more important matters. The hibernate session interface provides createcriteria method, which can be used to create a criteria object that returns instances of the persistence objects class when your application executes a criteria query. Projection of distinct value types and export to a dto class memory level, query of distinct entities using subqueries and restriction of type in database level query row count. It just gives you a different syntax, so criteria, both the create criteria and the queryover provide you just yet another querying mechanism that allows you to pull data out of the database using nhibernate.
This is an interface that extends the serializable. You may download log4net from, or install it with nuget. The solutions in nhibernates world, in accordance to the sql solutions. In this section we will show you, how to use the count query. Hql is how nhibernate exposes most of its power, and it allow you to operate on your domain model using set based, object oriented, language. Linq to a class library and split out the unit tests to a nhibernate. Ayende, this looks like a great start at getting linq for nhibernate going. Hibernate criteria projection distinct stack overflow. Cannot see the forum post at this moment broken link.
Oct 10, 2014 in our last hibernate lesson, you learned how to fix duplicate data from hibernate queries. To start working on nhibernate, we will need visual studio and the nhibernate package. Hibernate projection example projection in hibernate example. Nhibernate allows you to retrieve objects using your databases native sql dialect. For the rare cases where you cant make nhibernates own query facilities do exactly what you want. Its biggest weakness, however, is when you want to perform queries using some dynamic criteria.
In this post, ill show you how to get up and running with nhibernate in about 5. It seemed that all the introductory material i found was either very vague or so detailed that i got overwhelmed before getting to first base. Hibernate is popular open source object relational mapping tool for java platform. We can do this by adding an assembly, so by specifying the assembly. As we already discussed in the previous tutorial hibernate criteria, if we want to read a partial entity selected columns from the database, hibernate has provided us with a projection interface hibernate projection. Querying with nhibernate using queryover howtodoit. One of the more interesting ability of nhibernate is to selectively filter records based on some global filters. Mar 29, 2011 select distinct with nhibernate 29032011 by ajerrison leave a comment i found a blog post on stackoverflow about how to do the equivalent of sqls select distinct in nhibernate, but i cant seem to find it again so here is what i got from it. The nhibernate query by criteria api lets you build a query by manipulating criteria objects at runtime this approach lets you specify constraints dynamically without direct string manipulations, but it doesnt lose much of the flexibility or power of hql. The said hql query or an equivalent criteria is translated to the joined. Nhibernate removing duplicates combined with paging.
Net extension methods and you can get something quite neat. For more information on how to download and install this database, see here. Oct 31, 2007 the first step in using nhibernate is to download nhibernate and log4net, an opensource logging application that nhibernate can use to record errors and warnings. Future and futurevalue these two are more interesting. With this native query using isqlquery and the statement distinct is necessary because the union wiht t2 produces duplicate results of t. Nhibernate search transparently indexes your objects and offers fast regular, fulltext search. By continuing to use pastebin, you agree to our use of cookies as described in the cookies policy.
Whats important to note is that hibernate doesnt ever refer. In this tutorial, we are going to see hibernate projection with a simple example. Nhibernate can seem like a daunting library to set up. In this lesson were going to focus on some of the aggregate functions that can be used with hibernate, and of course that means diving into the group by clause. Hibernate count query in this section we will show you, how to use the count query. In this chapter, we will be covering criteria queries mechanism. Just as a reminder, the end goal is being able to use nhibernate to send this query in a single roundtrip to the database. Most classes will also have a property holding the unique identifier of an instance. How to query parent rows when all children must match the. Hibernate by example part 2 detachedcriteria dzone java. The following query has to be created using criteria. This tutorial uses the desktop edition sqlexpress, a free download from. Distinct query in criteria nhibernate stack overflow. Hibernate projections rowcount or countdistinct in this section, you will learn about the hibernate projection with an example.
If linq cant handle it, then you will start looking at hql or criteria to see if thats going to be more suitable. An objectoriented representation of a query result set projection in a criteria query. Annotation processor to generate jpa 2 static metamodel classes. Nhibernates powerful query facilities allow you to do almost anything you would in sql, and in some cases more. Nhibernate distinct by specific column example github. Nhibernate will be used by the repository and fluentnhibernate will be used for the mapping. This allow us to very easily create global where clauses that we can flip on and off at the touch of a switch. Getexecutingassembly and this is where program will find mapping files. Its similarity to sql means that it is often very intuitive when it comes the time to write and read it. It just gives you a different syntax, so criteria, both the create criteria and the queryover provide you just yet another querying mechanism that allows you. Once the downloading is completed then run the installer, then the following. Getting nhibernate up and running quickly andrew whitaker. We use cookies for various purposes including analytics.
In this example, we will discuss about hibernate criteria query, in this example we create a criteria instance and implement the factory methods for obtaining certain builtin criterion types method. Like i said, im using fluentnhibernate for the mapping. The configuration can get quite complicatedxml mappings, code mappings, mapping conventions, dialects, logging, etc. Nhibernate now knows how to connect to the database. Nov 27, 2009 nhibernate criteria api group by example non persisted class rob november 27, 2009 ive been working through the summer of nhibernate screen casts by steve bohlen. Distinct, order by and hibernate hql hedley proctor. Sometimes you just want to get something up and running to test out a query or play around with a database other than your primary one. In criteria api distinct clause can be applied by using following method of criteriaquery. This approach lets you specify constraints dynamically without direct string manipulations, but it doesnt lose much of the flexibility or power of hql. I would like to get a row count, but the method im using returns all objects and then gets the count of the collection. Entity framework e nhibernate o entity framework a maioria conhece. Jul 29, 2004 i need to write a query that returns all the distinct orders that match criteria b, where b could be anything from the date time created, to the order amount to the sku on the orderitem and i need to be able to order the results by any of the columns on the order class. This article grew out of my frustration trying to get started with nhibernate.