HQL查询实例

代码

using  System;
using  System.Collections.Generic;
using  System.Linq;
using  System.Text;
using  NHibernate;
using  NHibernate.Cfg;
using  DomainModel.Entities;
namespace  HQL
{
     public   class  QueryHQL
    {
         private  ISession _session;
         public  ISession Session
        {
             set
            {
                _session  =  value;
            }
        }
         public  QueryHQL(ISession session)
        {
            _session  =  session;
        }
         #region  基本语法学习
         ///   <summary>
         ///  from子句：简单用法
         ///   </summary>
         ///   <returns></returns>
         public  IList < Customer >  From()
        {
             // 返回所有Customer类的实例
             return  _session.CreateQuery( " from Customer " )
                .List < Customer > ();
        }
         ///   <summary>
         ///  from子句：使用别名
         ///   </summary>
         ///   <returns></returns>
         public  IList < Customer >  FromAlias()
        {
             // 返回所有Customer类的实例，Customer赋予了别名customer（as可以省略）
             return  _session.CreateQuery( " from Customer as customer " ).List < Customer > ();
        }
         ///   <summary>
         ///  from子句：笛卡尔积
         ///   </summary>
         ///   <returns></returns>
         public  IList < Customer >  FromCartesianproduct()
        {
             // 出现多个类，或者分别使用别名,返回笛卡尔积，或者称为“交叉”连接。
             return  _session.CreateQuery( " from Customer " )
                .List < Customer > ();
        }
         ///   <summary>
         ///  select子句：简单用法
         ///   </summary>
         ///   <returns></returns>
         public  IList < int >  Select()
        {
             // 返回在结果集中返回哪些对象和属性：返回所有Customer的CustomerId
             return  _session.CreateQuery( " select c.CustomerId from Customer c " )
                .List < int > ();
             // 注意：包括组件类型的属性select c.Name.Firstname from Customer c
        }
         ///   <summary>
         ///  select子句：数组
         ///   </summary>
         ///   <returns></returns>
         public  IList < object [] >  SelectObject()
        {
             // 用Object[]的数组返回多个对象和/或多个属性，或者使用特殊的elements功能，注意一般要结合group by使用
             return  _session.CreateQuery( " select c.Firstname, count(c.Firstname) from Customer c group by c.Firstname " )
                .List < object [] > ();
        }

         ///   <summary>
         ///  统计函数
         ///   </summary>
         ///   <returns></returns>
         public  IList < object [] >  AggregateFunction()
        {
             // 用Object[]的数组返回属性的统计函数的结果
             return  _session.CreateQuery( " select avg(c.CustomerId),sum(c.CustomerId),count(c) from Customer c " )
                .List < object [] > ();
             // 注意：统计函数的变量也可以是集合count( elements(c.CustomerId) )
        }
         ///   <summary>
         ///  Distinct用法
         ///   </summary>
         ///   <returns></returns>
         public  IList < string >  Distinct()
        {
             // distinct和all关键字的用法和语义与SQL相同。
             return  _session.CreateQuery( " select distinct c.Firstname from Customer c " )
                .List < string > ();
        }
         ///   <summary>
         ///  Where子句
         ///   </summary>
         ///   <returns></returns>
         public  IList < Customer >  Where()
        {
             // where子句让你缩小你要返回的实例的列表范围
             return  _session.CreateQuery( " select from Customer c where c.Firstname='YJing' " )
                .List < Customer > ();
             // where Order.Customer.Firstname is not null被翻译为带有一个表间（inner)join的SQL查询
             // 注意：where c.id=1 小写的id可以用来表示一个对象的惟一标识。（你可以使用它的属性名。）
             // 例如where Order.Customer.id=1 高效率,不需要进行表间连接
        }

         ///   <summary>
         ///  Where子句：表达式
         ///   </summary>
         ///   <returns></returns>
         public  IList < Customer >  WhereExpression()
        {
             return  _session.CreateQuery( " from Customer c where c.Firstname between 'A%' and 'Y%' " )
                .List < Customer > ();
             // 或者如下
             // from Customer c where c.Firstname not in ('YJing','Lee','li')
             // from Customer c where c.Firstname.size > 0 
        }
         ///   <summary>
         ///  order by子句
         ///   </summary>
         ///   <returns></returns>
         public  IList < Customer >  Orderby()
        {
             // 查询返回的列表可以按照任何返回的类或者组件的属性排序
             return  _session.CreateQuery( " select from Customer c order by c.Firstname asc,c.Lastname desc " )
                .List < Customer > ();
             // asc和desc是可选的，分别代表升序或者降序
        }
         ///   <summary>
         ///  group by子句
         ///   </summary>
         ///   <returns></returns>
         public  IList < object [] >  Groupby()
        {
             // 查询返回的列表可以按照任何返回的类或者组件的属性分组
             return  _session.CreateQuery( " select c.Firstname, count(c.Firstname) from Customer c group by c.Firstname " )
                .List < object [] > ();
        }
         ///   <summary>
         ///  子查询
         ///   </summary>
         ///   <returns></returns>
         public  IList < Customer >  Subquery()
        {
             return  _session.CreateQuery( " from Customer c where c.Lastname=some "
                 + " ( select c.Lastname from Customer c) " )
                .List < Customer > ();
        }
         #endregion  

         #region  实例学习
         ///   <summary>
         ///  按Firstname查询顾客
         ///   </summary>
         ///   <param name="firstname"></param>
         ///   <returns> 顾客列表 </returns>
         public  IList < Customer >  GetCustomersByFirstname( string  firstname)
        {
             // ISession _session = GetSession();

             // 写法1
             // return _session.CreateQuery("select from Customer c where c.Firstname='" + firstname + "'").List<Customer>();

             // 写法2
             // return _session.CreateQuery("select from Customer c where c.Firstname=?")
             //     .SetString(0, firstname)
             //     .List<Customer>();
            
             // 写法3
             return  _session.CreateQuery( " select from Customer c where c.Firstname=:fn " )
                .SetString( " fn " , firstname)
                .List < Customer > ();
        }
         ///   <summary>
         ///  按Firstname和Lastname查询顾客
         ///   </summary>
         ///   <param name="firstname"></param>
         ///   <param name="lastname"></param>
         ///   <returns> 顾客列表 </returns>
         public  IList < Customer >  GetCustomersByFirstnameAndLastname( string  firstname,  string  lastname)
        {
             return  _session.CreateQuery( " select from Customer c where c.Firstname=:fn and c.Lastname=:ln " )
                .SetString( " fn " , firstname)
                .SetString( " ln " , lastname)
                .List < Customer > ();
        }
         ///   <summary>
         ///  获取顾客ID大于CustomerId的顾客
         ///   </summary>
         ///   <param name="customerId"> 顾客ID </param>
         ///   <returns> 顾客列表 </returns>
         public  IList < Customer >  GetCustomersWithCustomerIdGreaterThan( int  customerId)
        {
             return  _session.CreateQuery( " select from Customer c where c.CustomerId > :cid " )
                .SetInt32( " cid " , customerId)
                .List < Customer > ();
        }

         public  IList < string >  GetDistinctCustomerFirstnames()
        {
             return  _session.CreateQuery( " select distinct c.Firstname from Customer c " )
                .List < string > ();
        }

         public  IList < Customer >  GetCustomersOrderedByLastnames()
        {
             return  _session.CreateQuery( " select from Customer c order by c.Lastname " )
                .List < Customer > ();
        }
         #endregion
    }
}