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HQL常用查詢
1.全選
      org.hibernate.Query query = session.createQuery("from Student");
      java.util.Iterator iterator = query.list().iterator();
      tx.commit();
      while (iterator.hasNext()){
             Student student = (Student)iterator.next();
             System.out.println("--------------------------------");
             System.out.println(student.getStudentId());
             System.out.println(student.getName());    
      }
       
注意:查詢語句中的不是表格名而是對象名,所以必須大寫
 
2.選擇
 (1)固定參數(shù)
      org.hibernate.Query query = session.createQuery("from Student s where s.name='朱紅'");
      java.util.Iterator iterator = query.list().iterator();
      tx.commit();
      while (iterator.hasNext()){
             Student student = (Student)iterator.next();
             System.out.println("--------------------------------");
             System.out.println(student.getStudentId());
             System.out.println(student.getName());    
}
 (2)位置參數(shù)
      org.hibernate.Query query = session.createQuery("from Student s where s.id=?");
      query.setParameter(0,"001");
      java.util.Iterator iterator = query.list().iterator();
      tx.commit();
      while (iterator.hasNext()){
             Student student = (Student)iterator.next();
             System.out.println("--------------------------------");
             System.out.println(student.getStudentId());
             System.out.println(student.getName());    
      }
 (3)命名參數(shù)
      org.hibernate.Query query = session.createQuery("from Student s where s.id=:student_id");
      query.setParameter("student_id","007");
      java.util.Iterator iterator = query.list().iterator();
      tx.commit();
3.投影
  org.hibernate.Query query = session.createQuery("select s.studentId,s.name from Student s ");
      java.util.Iterator iterator = query.list().iterator();
     
      while (iterator.hasNext()){
             Object[] row = (Object[])iterator.next();
             System.out.println("--------------------------------");
             System.out.println((String)row[0]);
}
 
//執(zhí)行的過程中存在奇怪的問題,只查詢一個表,只查詢一列時候才出現(xiàn)的錯誤,只要選擇兩列以上就沒問題了
//查詢兩個以上表格時,也存在該問題
 
4.連接
根據(jù)子類查找父類信息
org.hibernate.Query query = session.createQuery("select c.id,c.className from Zlass c inner join c.students s where s.studentId='001'");
java.util.Iterator iterator = query.list().iterator();
     
while (iterator.hasNext()){
             Object[] row = (Object[])iterator.next();
             System.out.println("--------------------------------");
             System.out.println((String)row[0]+(String)row[1]);
}
 
//根據(jù)父類查找子類
org.hibernate.Query query = session.createQuery("from Zlass c where c.id='971002'");
      java.util.Iterator iterator = query.list().iterator();
     
      while (iterator.hasNext()){
          Zlass row = (Zlass)iterator.next();
             java.util.Iterator i = row.getStudents().iterator();
             while(i.hasNext()){
                 Student s = (Student)i.next();
            System.out.println("--------------------------------");
            System.out.println(s.getStudentId()+" "+s.getName());
        }
      }
 //根據(jù)父類查找子類2,使用elements
 org.hibernate.Query query = session.createQuery("select elements(c.students) from Zlass c where c.id='971002'");
      java.util.Iterator iterator = query.list().iterator();
     
      while (iterator.hasNext()){
                 Student s = (Student)iterator.next();
            System.out.println("--------------------------------");
            System.out.println(s.getStudentId()+" "+s.getName());
      }
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