我的插入语句有什么问题？

Question

For some reason, I can only select data from a table but I can't insert.

Ie function nee() works fine, but wee() doesn't... It was working earlier today... anyone know the reason?

Class wtf{
    private $db;
    public function __construct(){
        $this->db = new Store_Connection();
        $this->db = $this->db->dbStore();
    }

    public function nee(){
        $st = $this->db->prepare("select paid from sales where id=14");
        $st->execute();
        $product = $st->fetch(PDO::FETCH_OBJ);
        print_r($product);
    }

    public function wee(){
        $st = $this->db->prepare("insert into sales(paid) values (sdf)");
        $st->execute();

    }

}

$work = new wtf();
$work->wee();

Answer 1

这样尝试

$st = $this->db->prepare("insert into sales(paid) values ('sdf')");

Answer 2

whats sdf? is it a text/string, then use ' around it