SQLException: ORA-02292: integrity constraint (SCHOOL.STUDENT_STAGE_FK) violated – child record found

Here i have a problem in my code when i want to delete a record:(student) from database and i know there is a related key
but i cannot solve this problem i tried deleting student that on the stage and this is the code:

public int deleteStudentStage(int stdId) //delete student by stId
{
    DatabaseConnection dbconn = new DatabaseConnection();
    Connection conn = dbconn.getConn();
    PreparedStatement pStm = null;
    int rows = 0;
    try
    {
        //String sql = "DELETE FROM STUDENT_STAGE WHERE STUDENT_ID = ? AND STAGE_ID = ?";

        String sql = "DELETE FROM STUDENT WHERE ID = ? ";

        pStm = conn.prepareStatement(sql);

        //fill SQL parameters from student: //
        pStm.setInt(1, stdId);

        // excute //
        rows = pStm.executeUpdate();
    }
    catch (SQLException ex) 
    {
        System.out.println("SQLException: " + ex.getMessage());
    }
     finally
    {
        try {
            conn.commit();
            pStm.close();
            conn.close();
        } catch (SQLException ex) {
            System.out.println("SQLException: " + ex.getMessage());;
        }
    }
    return rows;
}  

here the schema

Answer

can you give more information about it?, normally that happens when you have a foregin key, in this case of the table STUDENT, you need to delete all rows in the other table first before delete STUDENT, you also can solve it, adding a delete on cascade, when you create the foregin key

you need then do the following:

DELETE FROM STUDENT_STAGE WHERE STUDENT_ID=? 
DELETE FROM STUDENT WHERE ID = ? 

also you can update the foregin key in the table for cascade delete:

ALTER TABLE STUDENT_STAGE DROP FOREIGN KEY STUDENT_STAGE_FK; 
ALTER TABLE STUDENT_STAGE ADD CONSTRAINT STUDENT_STAGE_FK FOREIGN KEY STUDENT_ID REFERENCES STUDENT (ID) ON DELETE CASCADE ON UPDATE CASCADE;

Whith the update of the foregin key, deleting a studen, you also delete all the information of this student in the table STUDENT_STAGE