NHibernate - Native Sql

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In this chapter, we will be covering how to use the native SQL queries in NHibernate. If you have been using handwritten SQL for a number of years, you may be concerned that ORM will take away some of the expressiveness and flexibility you are used to.

  • NHibernate’s powerful query facilities allow you to do almost anything you would in SQL, and in some cases more.

  • For the rare cases where you can’t make NHibernate’s own query facilities do exactly what you want.

  • NHibernate allows you to retrieve objects using your database’s native SQL dialect.

Let’s have a look into a simple example of the Native SQL queries in NHibernate.

using System; 
using System.Data; 
using System.Linq; 
using System.Reflection; 

using HibernatingRhinos.Profiler.Appender.NHibernate; 
using NHibernate.Cfg; 
using NHibernate.Criterion; 
using NHibernate.Dialect; 
using NHibernate.Driver; 
using NHibernate.Linq; 
using NHibernate;

namespace NHibernateDemo {

   internal class Program { 
	
      private static void Main() { 
		
         var cfg = ConfigureNHibernate(); 
         var sessionFactory = cfg.BuildSessionFactory();
         using(var session = sessionFactory.OpenSession()) 
         
         using(var tx = session.BeginTransaction()) {
            IQuery sqlQuery = session.CreateSQLQuery("SELECT * FROM
               CUSTOMER").AddEntity(typeof(Customer));
            var customers = sqlQuery.List<Customer>();
				
            foreach (var customer in customers) { 
               Console.WriteLine(customer); 
            } 
				
            tx.Commit(); 
         }
         
         Console.WriteLine("Press <ENTER> to exit..."); 
         Console.ReadLine(); 
      }
		
      private static Configuration ConfigureNHibernate() { 
		
         NHibernateProfiler.Initialize(); 
         var cfg = new Configuration(); 
         
         cfg.DataBaseIntegration(x => { 
            x.ConnectionStringName = "default"; 
            x.Driver<SqlClientDriver>(); 
            x.Dialect<MsSql2008Dialect>(); 
            x.IsolationLevel = IsolationLevel.RepeatableRead; 
            x.Timeout = 10; 
            x.BatchSize = 10; 
         }); 
         
         cfg.SessionFactory().GenerateStatistics();
         cfg.AddAssembly(Assembly.GetExecutingAssembly()); 
         return cfg; 
      } 
   } 
}

The above example uses CreateSQLQuery() to get back a list of objects, and you will also notice that the root entity type you want the query to return is specified as Customer.

Let’s run your application and you will see that all the customers are retrieved from the database.

Emerson Prosacco (4ec2a0e0-6bce-11e1-b2cf-6cf049ee52be)
   Points: 17
   HasGoldStatus: False
   MemberSince: 6/22/2007 12:00:00 AM (Utc)
   CreditRating: Excellent
   AverageRating: 0

   Orders:
      Order Id: 4ec2a0e0-6bce-11e1-b2d0-6cf049ee52be
      Order Id: 4ec2a0e0-6bce-11e1-b2d1-6cf049ee52be
      Order Id: 4ec2a0e0-6bce-11e1-b2d2-6cf049ee52be
      Order Id: 4ec2a0e0-6bce-11e1-b2d3-6cf049ee52be
      Order Id: 4ec2a0e0-6bce-11e1-b2d4-6cf049ee52be

Kaci Friesen (4ec2a0e0-6bce-11e1-b2d5-6cf049ee52be)
   Points: 30
   HasGoldStatus: True
   MemberSince: 5/25/2007 12:00:00 AM (Utc)
   CreditRating: VeryVeryGood
   AverageRating: 0

   Orders:
      Order Id: 4ec2a0e0-6bce-11e1-b2d6-6cf049ee52be
      Order Id: 4ec2a0e0-6bce-11e1-b2d7-6cf049ee52be
      Order Id: 4ec2a0e0-6bce-11e1-b2d8-6cf049ee52be
      Order Id: 4ec2a0e0-6bce-11e1-b2d9-6cf049ee52be
      Order Id: 4ec2a0e0-6bce-11e1-b2da-6cf049ee52be
      Order Id: 4ec2a0e0-6bce-11e1-b2db-6cf049ee52be

Eveline Waters (4ec2a0e0-6bce-11e1-b2dc-6cf049ee52be)
   Points: 58
   HasGoldStatus: False
   MemberSince: 10/29/2009 12:00:00 AM (Utc)
   CreditRating: Good
   AverageRating: 0

   Orders:
      Order Id: 4ec2a0e0-6bce-11e1-b2dd-6cf049ee52be
      Order Id: 4ec2a0e0-6bce-11e1-b2de-6cf049ee52be
      Order Id: 4ec2a0e0-6bce-11e1-b2df-6cf049ee52be
      Order Id: 4ec2a0e0-6bce-11e1-b2e0-6cf049ee52be
      Order Id: 4ec2a0e0-6bce-11e1-b2e2-6cf049ee52be

Molly Kuhn (4ec2a0e0-6bce-11e1-b2e3-6cf049ee52be)
   Points: 73
   HasGoldStatus: False
   MemberSince: 12/16/2007 12:00:00 AM (Utc)
   CreditRating: VeryGood
   AverageRating: 0

   Orders:
      Order Id: 4ec2a0e0-6bce-11e1-b2e4-6cf049ee52be
      Order Id: 4ec2a0e0-6bce-11e1-b2e5-6cf049ee52be
      Order Id: 4ec2a0e0-6bce-11e1-b2e6-6cf049ee52be
      Order Id: 4ec2a0e0-6bce-11e1-b2e7-6cf049ee52be
      Order Id: 4ec2a0e0-6bce-11e1-b2e8-6cf049ee52be
      Order Id: 4ec2a0e0-6bce-11e1-b2e9-6cf049ee52be
      Order Id: 4ec2a0e0-6bce-11e1-b2ea-6cf049ee52be
      Order Id: 4ec2a0e0-6bce-11e1-b2eb-6cf049ee52be
      Order Id: 4ec2a0e0-6bce-11e1-b2ec-6cf049ee52be

Here is another way of writing native SQL query as shown below.

IList<Customer> customers = session.CreateSQLQuery("SELECT * FROM CUSTOMER")
   .AddScalar("Id", NHibernateUtil.Guid) 
   .AddScalar("FirstName", NHibernateUtil.String) 
   .AddScalar("LastName", NHibernateUtil.String) .List<Customer>();

  • As you can see that the above query specified the SQL query string and the columns and types to return.

  • This will return an IList of Object arrays with scalar values for each column in the Customer table.

  • Only these three columns will be returned, even though the query is using * and could return more than the three listed columns.

Let’s have a look into another simple example.

IList<Customer> customers = session.CreateSQLQuery("SELECT * FROM CUSTOMER WHERE  
   FirstName = 'Laverne'") 
   .AddEntity(typeof(Customer)) .List<Customer>(); 
	
foreach (var customer in customers) { 
   Console.WriteLine(customer); 
}

Let’s run your application again and you will see the following output.

Laverne Hegmann (4e97c816-6bce-11e1-b095-6cf049ee52be)
   Points: 74
   HasGoldStatus: True
   MemberSince: 4/4/2009 12:00:00 AM (Utc)
   CreditRating: Neutral
   AverageRating: 0

   Orders:
      Order Id: 4ea14d96-6bce-11e1-b095-6cf049ee52be
      Order Id: 4ea14d96-6bce-11e1-b096-6cf049ee52be
      Order Id: 4ea14d96-6bce-11e1-b097-6cf049ee52be
      Order Id: 4ea14d96-6bce-11e1-b098-6cf049ee52be
		
Press <ENTER> to exit...

Similarly, you can specify any type of SQL query to retrieve data from the database.

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