Encrypted password verification

I'm having a hard time checking the login with Delphi with encrypted password in the MySQL database, I can do the registration and encrypt the password in the database through Delphi with the StoredProcedure that I created in MySQL , this encryption made through the MD5 function of the MySQL itself. In Delphi , use TSQLStoredProc to use StoredProcedure of database.

The difficulty is in the% of% I created in Function , it returns an integer. If it is Mysql return:

zero

If it is o login está incorreto :

o login está certo 

um works correctly on Function , makes the correct comparison, however, what I do not know is how do I show or compare this MySQL with that integer return on Function .

Here is my code for you to understand:

SQL:

DELIMITER $$ 
 CREATE TABLE 'tbl_users' ( 
  'id' int(11) NOT NULL AUTO_INCREMENT, 
  'username' varchar(15) NOT NULL, 
  'firstlast_name' varchar(80) DEFAULT NULL, 
  'password' varchar(45) DEFAULT NULL, 
  PRIMARY KEY ('id') 
)$$ 
 DELIMITER ; 

 DELIMITER $$  
 DROP FUNCTION IF EXISTS 'fun_valida_usuario'$$  
 CREATE FUNCTION 'fun_valida_usuario'(p_username VARCHAR(15)  
                , p_password VARCHAR(45) ) RETURNS INT(1)  
 BEGIN  
 DECLARE _ret            INT(1) DEFAULT 0;  
     SET _ret = IFNULL((SELECT DISTINCT 1  
                       FROM tbl_users  
                      WHERE 'username' = p_username  
                       AND 'password' = MD5(p_password)),0);                            
 RETURN _ret;  
 END$$  
 DELIMITER ; 

DELIMITER $$ 
CREATE PROCEDURE 'proc_iae_tbl_users'( 
p_opc varchar(1), 
p_id int, 
p_username varchar(15), 
p_firstlast_name varchar(80), 
p_password varchar(45)) 
BEGIN 

IF ((p_opc = 'I') && (p_username != '') && (p_password != '')) THEN 

  INSERT INTO tbl_users (id, username, firstlast_name, 'password') VALUES (p_id, p_username, p_firstlast_name, MD5(p_password)); 

ELSE 

IF ((p_opc = 'E') && (p_id > 0)) THEN 

   delete from tbl_users where id = p_id; 

ELSE 

IF ((p_opc = 'A')) THEN 

  UPDATE tbl_users set id = p_id, username = p_username, firstlast_name = p_firstlast_name, 'password' = p_password WHERE id = p_id; 

ELSE 
SELECT 'Você não pode realizar as alterações' AS Msg; 
END IF; 
END IF; 
END IF; 

END$$ 
DELIMITER ; 

PAS:

unit Unit1; 

interface 

uses 
  Windows, Messages, SysUtils, Variants, Classes, Graphics, Controls, Forms, 
  Dialogs, WideStrings, DBXMySql, DB, SqlExpr, FMTBcd, Provider, DBClient, 
  StdCtrls, Mask, DBCtrls; 

type 
  TForm1 = class(TForm) 
    SQLConnection1: TSQLConnection; 
    ClientDataSet1: TClientDataSet; 
    DataSetProvider1: TDataSetProvider; 
    SQLQuery1: TSQLQuery; 
    SQLQuery1id: TIntegerField; 
    SQLQuery1username: TStringField; 
    SQLQuery1firstlast_name: TStringField; 
    SQLQuery1password: TStringField; 
    DataSource1: TDataSource; 
    ClientDataSet1id: TIntegerField; 
    ClientDataSet1username: TStringField; 
    ClientDataSet1firstlast_name: TStringField; 
    ClientDataSet1password: TStringField; 
    InsertUser: TButton; 
    Edit1: TEdit; 
    Edit2: TEdit; 
    proc_iae_tbl_users: TSQLStoredProc; 
    proc_iae_tbl_usersMsg: TStringField; 
    Edit3: TEdit; 
    Edit4: TEdit; 
    Edit5: TEdit; 
    VerifyLogin: TButton; 
    Label1: TLabel; 
    Label2: TLabel; 
    SQLStoredProc1: TSQLStoredProc; 
    SQLStoredProc1Value: TIntegerField; 
    Label3: TLabel; 
    DBEdit1: TDBEdit; 
    DataSource2: TDataSource; 
    SQLQuery2: TSQLQuery; 
    SQLQuery2Valor: TIntegerField; 
    Label4: TLabel; 
    DBEdit2: TDBEdit; 
    DataSource3: TDataSource; 
    procedure Button1Click(Sender: TObject); 
    procedure Button2Click(Sender: TObject); 
  private 
    { Private declarations } 
  public 
    { Public declarations } 
  end; 

var 
  Form1: TForm1; 

implementation 

{$R *.dfm} 

procedure TForm1.InsertUserClick(Sender: TObject); 
begin 
   proc_iae_tbl_users.Close; 
   proc_iae_tbl_users.ParamByName('p_opc').Value:= 'I'; 
   proc_iae_tbl_users.ParamByName('p_username').Value:= Edit1.Text; 
   proc_iae_tbl_users.ParamByName('p_firstlast_name').Value:= Edit2.Text; 
   proc_iae_tbl_users.ParamByName('p_password').Value:= Edit3.Text; 
   proc_iae_tbl_users.ExecProc; 
end; 

procedure TForm1.VerifyLoginClick(Sender: TObject); 
begin 
   // Aqui deve ficar o código para logar e verificar o login 
end; 

end.

Can someone give me a solution?

Thank you for your prompt delivery. Thank you.