The basic common small examples of hql in Hibernate, single table query and multiple table query

<span style= "Font-size:24px;color: #3366ff;" > This article implements the following functions of HQL:</span>
/**
 * HQL Syntax:
 *   1) Single table query
 *   	 1.1 Full Table Query
 *       1.2 Specify field query
 *       1.3 excluding duplicate records
 *       1.4 piece Query (emphasis)
 *       1.5 paging Query
 *       1.6 aggregation Query
 *       1.7 query Sort
 *       1.8 Group Inquiry
 *       1.9 After grouping filter
 *       
 *   2 Multi-table Query
 *       1.1 Inner Connection
 *       1.2 left outer/right outer connection   
* *
</span>

First, you configure the hibernate XML file so that two databases are linked, a one-to-many mapping connection

Employee.hbm.xml

<?xml version= "1.0" encoding= "UTF-8"?> <!
DOCTYPE hibernate-mapping Public "-//hibernate/hibernate mapping DTD 3.0//en" "http://hibernate.sourceforge.net/ Hibernate-mapping-3.0.dtd ">
 

 



Dept.hbm.xml


<?xml version= "1.0" encoding= "UTF-8"?> <!
DOCTYPE hibernate-mapping Public "-//hibernate/hibernate mapping DTD 3.0//en" "http://hibernate.sourceforge.net/ Hibernate-mapping-3.0.dtd ">
 

 

 

Create two more entity classes

Employee.java


Package star.july.d_hql;
	public class Employee {private int id;
	private String name;
	Private String gender;
	Private String title;
	Private String Email;
	private double salary;
	
	Private Dept Dept = new Dept ();
	Public Dept getdept () {return Dept;
	public void Setdept (Dept Dept) {this.dept = Dept;
	public int getId () {return id;
	The public void setId (int id) {this.id = ID;
	Public String GetName () {return name;
	public void SetName (String name) {this.name = name;
	Public String Getgender () {return gender;
	} public void Setgender (String gender) {This.gender = gender;
	Public String GetTitle () {return title;
	public void Settitle (String title) {this.title = title;
	Public String Getemail () {return email;
	public void Setemail (String email) {this.email = email;
	Public double getsalary () {return salary;
	The public void Setsalary (double salary) {this.salary = salary;
	@Override public String toString () {	Return "Employee [id= + ID +", name= "+ name +", gender= "+ Gender +", title= "+ title +", email= "+ email +",
	Salary= "+ salary +"];
 }
	
	
}
 

 

 





Dept.java


Package star.july.d_hql;

Import Java.util.HashSet;
Import Java.util.Set;

public class Dept {
	private int id;
	Private String deptname;
	Private set<employee> Employee = new hashset<employee> ();
	public int getId () {return
		ID;
	}
	public void setId (int id) {
		this.id = ID;
	}
	Public String Getdeptname () {return
		deptname;
	}
	public void Setdeptname (String deptname) {
		this.deptname = deptname;
	}
	Public set<employee> GetEmployee () {return
		Employee;
	}
	public void Setemployee (Set<employee> employee) {
		This.employee = employee;
	}
	
	
}	
 

 

 



Final Test HQL:

Demo.java


Package star.july.d_hql;
Import java.util.List;

Import Java.util.Set;
Import Org.hibernate.Query;
Import org.hibernate.Session;
Import org.hibernate.Transaction;

Import Org.junit.Test;
Import Star.july.util.HibernateUtil;
 /** * HQL Grammar: * 1) Single table query * 1.1 Full Table Query * 1.2 Specify field Query * 1.3 excluding duplicate records * 1.4 piece Query (emphasis) * 1.5 paging query * 1.6 Aggregate Query * 1.7 Query Sort * 1.8 Group Inquiry * 1.9 Group after filter * * 2) Multi-table Enquiry * 1.1 Inner link * 1 .2 LEFT OUTER join/RIGHT OUTER JOIN * */public class Demo {@Test public void Test () {Session session = Hibernateutil.get
		Session ();
		Transaction ts = session.gettransaction ();
			try{Ts.begin ();
			HQL basic syntax//1, create a Query object//parameter: HQL statement String hql = "Select E from Employee e where id = 1";
			Query query = session.createquery (HQL);
			2. Execute Query//2, 1 package all list<employee> emp = Query.list ();
			for (Employee e:emp) {System.out.println (e); }//2, 2 package one (first) employee Empl = (employee) qUery.uniqueresult ();
			
			System.out.println (EMPL);
			
		Ts.commit ();
			}catch (Exception e) {e.printstacktrace ();
		Ts.rollback ();
		}//Tanku query @Test public void Test3 () {Session session = Hibernateutil.getsession ();
		Transaction ts = session.gettransaction (); try{Ts.begin ();//* 1) Single table query//* 1.1 Full Table Query//String HQL = "from STAR.JULY.D_HQL.
			Employee ";
			
Auto-import: Automatically to burst, automatically under each package to search for the corresponding class of packages, multiple classes of the same name of the report conflict//String HQL = "Select E from Employee e";
			
* 1.2 Specify field query//return object array//String HQL = "Select E.name,e.title from Employee e";
			
* 1.3 excluding duplicate records//String HQL = "SELECT DISTINCT (e.gender) from Employee e"; * 1.4 piece Query (emphasis) (where)//logical conditions: and OR//fuzzy query: like:% _//Comparison query: < > <= >= between and <
>//NULL query: Is NULL, are not null, = ',<> ';
String hql = "Select E from Employee e where name like ' Zhang% '"; String hql = "Select E from Employee e where e.gender is null or e.geNder= ' ";
			* 1.5 Paging query/* String HQL = "from Employee";
			Query query = session.createquery (HQL);
			Set start reading row query.setfirstresult (0); How many messages per page query.setmaxresults (3); *///* 1.6 aggregate query//avg,count,max,min,uniqueresult//String HQL =
			
"Select Max (e.salary) from Employee e";
			
			
* 1.7 Query sort//order by//desc: Descending ASC: Ascending//String HQL = "Select E from Employee e-id desc";
		
* 1.8 grouped query//String HQL = "Select e from Employee e Group by E.gender";  * 1.9 After grouping filter String hql = "Select E from Employee e where e.gender are not null and e.gender<> ' group"
			
			by E.gender has count (e.gender) >1 ";
			
			
			Query query = session.createquery (HQL);
			Collection Object List<object> e = Query.list ();
			for (Object emp:e) {System.out.println (EMP);
			}//Object array/* list<object[]> objects = query.list (); For (object[] object:objects) {for (Object Obj:objeCT) {System.out.print (obj);
			} System.out.println ();
			*//Encapsulate an object/*object unique = Query.uniqueresult ();
		System.out.println (unique); */Ts.commit ();
			}catch (Exception e) {e.printstacktrace ();
		Ts.rollback ();
			}//Multiple table query @Test public void Test2 () {Session session = Hibernateutil.getsession ();
			Transaction ts = session.gettransaction ();
				
				try{Ts.begin (); /** * Step * 1, determine which objects to query *2, determine what to wipe out what properties * 3, determine the connection conditions *4, business conditions * *//1, the Internal Connection query//effect: Only the data to meet the conditions will be displayed 
				Come out/check employees and their departments: Show employee name, department name//String HQL = "Select E.name,d.deptname from Employee E, Dept D where e.dept.id=d.id";
				
				
				Another way of writing//String hql = "Select E.name,d.deptname from Employee e inner join e.dept d"; Left OUTER JOIN//Effect: First display left table, right table data match display, mismatched then show null//query All Department employees (departments that do not have employees to display) String hql = "Select D.deptname, E.name fro
				
				M Dept D left outer join D.employee E "; Right outer join//String HQL = "Select D.deptname,e.name from Employee e right outer join e.dept D ";
				
				Query query = session.createquery (HQL);
				/*list<object> Object = Query.list ();
				for (Object obj:object) {System.out.println (obj);
				}*/list<object[]> objects = Query.list ();
					For (object[] object:objects) {for (Object obj:object) {System.out.print (obj);
				} System.out.println ();
				
			} ts.commit ();
				}catch (Exception e) {e.printstacktrace ();
			Ts.rollback ();
 }
		}
}