[android help] sqlite statement is ok, right?

When I use the sentence below works fine!

this.getWritableDatabase().execSQL(
  "UPDATE table SET assistance =assistance + 1 WHERE alum ='Saul'");

But when I tried doing it passing a variable like this:

this.getWritableDatabase().execSQL(
  "UPDATE table SET assistance =assistance + 1 WHERE alum ='"+names[i]+"'");

Don't work at all : ( it does not hive me any errors but my assistance field don't goes up by 1, by the way the statement above is inside a loop, that's because I want to update all the assistance fields that match whit my names (names[i]). Sorry for my English and please help

//edit:

so here is the method event from one activity that tigger the helper method

public void pasar(View args){

    choosennames= new String[500];
    for(int i=0;i

        TextView viewName= (TextView) findViewById(i);
    //an array names 
    names.add(viewName);


    } 

    for( j = 0;j     obj= name.get(j);



         for(k=0;k          if(obj.getId()==num.get(k))
          {

            choosennames[z]=obj.getText().toString();  

            z++;
          }
               }
    } 

     z=0;
    helper.open();
    howmany=num.size();
    helper.mod(choosennames, howmany);
    helper.close();
    choosennames=null;


    Iterator it = numeros.iterator(); //se crea el iterador it para el array 
    while(it.hasNext())                    
            System.out.println(it.next()); 




    Intent inten = new Intent(this, MainLista.class);
      this.finish();

      Toast toast1 =
                Toast.makeText(getApplicationContext(),
                        "Pase de lista exitoso : )", Toast.LENGTH_SHORT);

            toast1.show();
   startActivity(inten);





}

And finally this is my method "mod" inside the helpers class:

public void mod(String []names,int howmany){

    for(int i=0;i        System.out.println("exectSQL:"+names[i]);

        System.out.println("UPDATE alumnos SET asistencia =asistencia + 1 WHERE alumno ='"+names[i]+"'");

        this.getWritableDatabase().execSQL(
                "UPDATE alumnos SET asistencia =asistencia + 1 WHERE alumno ='"+names[i]+"'");



    }




}

.

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