將查詢值從變量設置為null

Question

我正在嘗試使用PDO將空值插入數據庫中，但似乎有問題

碼

public function addBookCategory($id, $isbn, $category, $parent){
    $id = $this->dbh->quote($id);
    $isbn = $this->dbh->quote($isbn);
    $category = $this->dbh->quote($category);
    $parent = $this->dbh->quote($parent);

    return $this->query(
        "INSERT INTO book_categories 
        VALUES($id, $isbn, $category, $parent) 
        ON DUPLICATE KEY UPDATE id = $id"
    );
}

在某些情況下，父列可以為null，但是以下任何一個都不會將parent設置為null，而是將值設置為空字符串“”或空字符串“ NULL”。

$database->addBookCategory("kujhg", "asdasd", "asdasd", NULL);
$database->addBookCategory("kujhg", "asdasd", "asdasd", "");
$database->addBookCategory("kujhg", "asdasd", "asdasd", "NULL");

如何解決這個問題？

Answer 1

你應該寫列名

   "INSERT INTO book_categories (id, isbn , category,parent)
    VALUES($id, $isbn, $category, $parent) 
    ON DUPLICATE KEY UPDATE id = $id"

然后用這個

  $database->addBookCategory("kujhg", "asdasd", "asdasd", NULL);