Oracle问题：为什么在PLSQL Developer中可以查询出结果集，但用jdbc无法查询？

Question

create table SDM(
  dno char(4),
  sname varchar2(9),
  primary key(dno,sname)
);

create table MDP(
  week char(2),
  dno char(4),
  dnum smallint default 0,
  rnum smallint default 0,
  sname varchar2(9) not null,
  rdate date default sysdate,
  primary key(week,dno),
  foreign key (dno,sname) references SDM(dno,sname)
);

在PLSQL Developer中执行语句：
select * from mdp where week='1' and dno='4426';
可以查询到结果集，
但是使用jdbc无法查询到结果集
@Override
    public MDP getMDP(String week, String dno) {
        MDP mdp = null;
        try {
            conn = DatabaseBean.getConnection();
            String sql = "select * from mdp where week=? and dno=?";
            psmt = conn.prepareStatement(sql);
            psmt.setString(1, week);
            psmt.setString(2, dno);
            rs = psmt.executeQuery();
            if (rs.next()) {
                mdp = new MDP();
                mdp.setWeek(rs.getString("week"));
                mdp.setDno(rs.getString("dno"));
                mdp.setDnum(rs.getInt("dnum"));
                mdp.setRnum(rs.getInt("rnum"));
                mdp.setSname(rs.getString("sname"));
                Timestamp ACTDATETIME = rs.getTimestamp("rdate");
                SimpleDateFormat nu = new SimpleDateFormat("YYYY-MM-dd HH:mm:ss");
                mdp.setRdate(nu.format(ACTDATETIME));
            }
        } catch (SQLException e) {
            e.printStackTrace();
        } finally {
            DatabaseBean.close(rs, psmt, conn);
        }
        return mdp;
    }

        1   4426    0   0   李二  2020-05-31 11:20:05记录已存在
        运行以下代码显示该记录不存在，记录本身就存在但是查询不出来

        String week = "1";
        String dno = "4426";

        MDP mdp = DaoFactory.getMDPDao().getMDP(week.trim(), dno.trim());
        if (mdp != null) {
            String errValue = mdp.getDno() + " 宿舍的 " + mdp.getSname() + " 同学在第" + mdp.getWeek() + " 周已领取抗疫物资口！";
            System.out.println("该记录存在");
        }else{
            System.out.println("该记录不存在");
        }

Answer 1

root用户进Developer里设置下 root账户对这个database的权限，重新grant，再flush下