How to retrieve value from databases and compare it to string

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Java

JDBC

MySQL

hi. i want to create login page that only user who had role as admin can login. here is my databases :

tb_users :
user_id (PK, string)
password

tb_user_auth :
user_id (FK,string)
objects_id // contain user's role(string)

the problem is it seems like i retrieve nothing from objects_id so there's message like this : "check your password and user id". would you kindly tell me what's wrong with my code?

What I have tried:

private void cmd_loginActionPerformed(java.awt.event.ActionEvent evt) {
try{
String sql = "select * from tb_users where user_id=? and password=?";
PST=conn.prepareStatement(sql);
PST.setString(1,txt_userid.getText());
PST.setString(2, txt_pass.getText());
RS=PST.executeQuery();
RS.close();


String sql2 = "select * from tb_userauth";
PST=conn.prepareStatement(sql2);
//PST.setString(1,txt_userid.getText());
RS=PST.executeQuery();
//String objek_id = null;



if(RS.next()){
String objek = "admin";
String objek_id = RS.getString("objects_id");

if (objek_id.equals(objek)){

JOptionPane.showMessageDialog(null,"user id and password correct");
submenu1 sm1 = new submenu1();
sm1.setVisible(true);
sm1.pack();
sm1.setLocationRelativeTo(null);
sm1.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
this.dispose();
}else{
JOptionPane.showMessageDialog(null,"check your password and user id ");
} }

}catch (Exception e){
JOptionPane.showMessageDialog(null,e);
}


}