I just started learning hibernate. I read some theory and trying to implement one example using discriminator. Please help me in resolving this issue.

person.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">
<!-- column is DB-TABLE field name -->
<hibernate-mapping>
<class name="com.spwh.Person" table="PERSON" discriminator-value="P">
<id name="pid" column="PID">
<generator class="increment" />
</id>
<discriminator column="PERSONTYPE" type="string" />
<property name="firstName" column="FIRSTNAME" type="string" />
<property name="lastName" column="LASTNAME" type="string" />
<property name="ssn" column="SSN" type="int" />
<subclass name="com.spwh.Student" discriminator-value="S">
<property name="stdId" column="STDID" type="int" />
<property name="entranceDate" column="ENTRANCEDATE" type="date" />
</subclass>
<subclass name="com.spwh.Teacher" discriminator-value="T">
<property name="major" column="MAJOR" type="string" />
<property name="degree" column="DEGREE" type="string" />
</subclass>
</class>
</hibernate-mapping>

Person.java
-----------
package com.spwh;

import java.io.Serializable;

public class Person implements Serializable {
private int pid;
private String firstName;
private String lastName;
private int ssn;
private String personType;//discriminator column

public Person() {

}

public String getFirstName() {
return firstName;
}
public void setFirstName(String firstName) {
this.firstName = firstName;
}
public String getLastName() {
return lastName;
}
public void setLastName(String lastName) {
this.lastName = lastName;
}
public int getSsn() {
return ssn;
}
public void setSsn(int ssn) {
this.ssn = ssn;
}

public String getPersonType() {
return personType;
}
public void setPersonType(String personType) {
this.personType = personType;
}
public int getPid() {
return pid;
}

public void setPid(int pid) {
this.pid = pid;
}
}

Student.java
-------------
package com.spwh;

import java.util.Date;

public class Student extends Person {
private int stdId;
private Date entranceDate;

public Student() {

}
public int getStdId() {
return stdId;
}
public void setStdId(int stdId) {
this.stdId = stdId;
}
public Date getEntranceDate() {
return entranceDate;
}
public void setEntranceDate(Date entranceDate) {
this.entranceDate = entranceDate;
}
}

Teacher.java
--------------
package com.spwh;

public class Teacher extends Person {
private String major;
private String degree;

public Teacher() {

}

public String getMajor() {
return major;
}
public void setMajor(String major) {
this.major = major;
}
public String getDegree() {
return degree;
}
public void setDegree(String degree) {
this.degree = degree;
}
}

student table data:
------------------
ID FIRST_NAME LAST_NAME
1 KIRAN G
2 PADMAJA G
3 PRAMOD V
4 HARI B
5 BALAJI G

Person table data:
-----------------
PID FIRSTNAME LASTNAME SSN STDID ENTRANCEDT MAJOR DEGREE PERSONTYPE
1 Balajip Gp 123 5 0000-00-00 N MCA S
2 Kiranp Gp 456 1 0000-00-00 Y MBA T

persoan table STDID and student table ID FK relation

error when running the below main method:
main() {
//hibernate configuration ...
//tran starts in session...
Person p = (Person)session.load(Person.class, new Integer(1));
//tran comitt
}

error:
org.hibernate.exception.SQLGrammarException: could not load an entity: [com.spwh.Person#1]
at org.hibernate.exception.SQLStateConverter.convert(SQLStateConverter.java:65)
at org.hibernate.exception.JDBCExceptionHelper.convert(JDBCExceptionHelper.java:43)
at org.hibernate.loader.Loader.loadEntity(Loader.java:1799)
at org.hibernate.loader.entity.AbstractEntityLoader.load(AbstractEntityLoader.java:93)
at org.hibernate.loader.entity.AbstractEntityLoader.load(AbstractEntityLoader.java:81)
at org.hibernate.persister.entity.AbstractEntityPersister.load(AbstractEntityPersister.java:2730)
at org.hibernate.event.def.DefaultLoadEventListener.loadFromDatasource(DefaultLoadEventListener.java:365)
at org.hibernate.event.def.DefaultLoadEventListener.doLoad(DefaultLoadEventListener.java:346)
at org.hibernate.event.def.DefaultLoadEventListener.load(DefaultLoadEventListener.java:123)
at org.hibernate.event.def.DefaultLoadEventListener.onLoad(DefaultLoadEventListener.java:82)
at org.hibernate.impl.SessionImpl.fireLoad(SessionImpl.java:891)
at org.hibernate.impl.SessionImpl.immediateLoad(SessionImpl.java:849)
at org.hibernate.proxy.AbstractLazyInitializer.initialize(AbstractLazyInitializer.java:62)
at org.hibernate.proxy.AbstractLazyInitializer.getImplementation(AbstractLazyInitializer.java:98)
at org.hibernate.proxy.CGLIBLazyInitializer.intercept(CGLIBLazyInitializer.java:158)
at com.spwh.Person$$EnhancerByCGLIB$$8db8c258.toString(<generated>)
at java.lang.String.valueOf(Unknown Source)
at java.io.PrintStream.println(Unknown Source)
at com.spwh.ch03.PersistByHibernate.main(PersistByHibernate.java:87)
Caused by: com.mysql.jdbc.exceptions.jdbc4.MySQLSyntaxErrorException: Unknown column 'person0_.ENTRANCEDATE' in 'field list'
at sun.reflect.NativeConstructorAccessorImpl.newInstance0(Native Method)
at sun.reflect.NativeConstructorAccessorImpl.newInstance(Unknown Source)
at sun.reflect.DelegatingConstructorAccessorImpl.newInstance(Unknown Source)
at java.lang.reflect.Constructor.newInstance(Unknown Source)
at com.mysql.jdbc.Util.handleNewInstance(Util.java:406)
at com.mysql.jdbc.Util.getInstance(Util.java:381)
at com.mysql.jdbc.SQLError.createSQLException(SQLError.java:1030)
at com.mysql.jdbc.SQLError.createSQLException(SQLError.java:956)
at com.mysql.jdbc.MysqlIO.checkErrorPacket(MysqlIO.java:3491)
at com.mysql.jdbc.MysqlIO.checkErrorPacket(MysqlIO.java:3423)
at com.mysql.jdbc.MysqlIO.sendCommand(MysqlIO.java:1936)
at com.mysql.jdbc.MysqlIO.sqlQueryDirect(MysqlIO.java:2060)
at com.mysql.jdbc.ConnectionImpl.execSQL(ConnectionImpl.java:2542)
at com.mysql.jdbc.PreparedStatement.executeInternal(PreparedStatement.java:1734)
at com.mysql.jdbc.PreparedStatement.executeQuery(PreparedStatement.java:1885)
at org.hibernate.jdbc.AbstractBatcher.getResultSet(AbstractBatcher.java:139)
at org.hibernate.loader.Loader.getResultSet(Loader.java:1669)
at org.hibernate.loader.Loader.doQuery(Loader.java:662)
at org.hibernate.loader.Loader.doQueryAndInitializeNonLazyCollections(Loader.java:224)
at org.hibernate.loader.Loader.loadEntity(Loader.java:1785)
... 16 more

}

As the exception say: Caused by: com.mysql.jdbc.exceptions.jdbc4.MySQLSyntaxErrorException: Unknown column 'person0_.ENTRANCEDATE' in 'field list'

You have a ENTRANCEDT column in your DBMS but no ENTRANCEDATE.

Thanks "Newbie". I will check and let you know.