Ejemplos prepare

$sql="insert into actor (first_name,last_name) values (:first_name,:last_name)";
    $parametros=[
      'first_name'=>'Perico',
      'last_name'=>'De los palotes'
    ];
    $st=$conn->prepare($sql);
    $st->execute($parametros);
 $sql="SELECT city FROM country join city using(country_id) where country=:country";
   $parametros=[
       'country'=>'Argentina'
   ];
   $st=$conn->prepare($sql);
   $st->execute($parametros);
   $ciudades=$st->fetchAll();
   print_r($ciudades);
  $sql="SELECT country FROM country  where country like :country";
   $parametros=[
       'country'=>'%ar%'
   ];
   $st=$conn->prepare($sql);
   $st->execute($parametros);
   $paises=$st->fetchAll();
   print_r($paises);
 $sql = "SELECT * FROM customer join address using(address_id)
            where email=:email and phone=:phone";
   
  $parametros=[
        'email'=>'mary.smith@sakilacustomer.org',
        'phone'=>'28303384290'
    ];
    $st=$conn->prepare($sql);
    $st->execute($parametros);
    $cliente=$st->fetch();
    if (empty($cliente)){
        echo "No sé quién eres";
    } else{
        echo "hola ".$cliente['first_name'];
    }

    $sql="update film set replacement_cost=replacement_cost*:descuento where rating=:rating";
    $parametros=[
        'descuento'=>0.9,
        'rating'=>'R'
    ];
    $st=$conn->prepare($sql);
    $st->execute($parametros);