php - mysql select something 因为 where is not null

Question

我对此很陌生，所以我对 MySQL 有疑问。我在 openCart 中有查询:

$sql = "SELECT cp.category_id AS category_id,
           GROUP_CONCAT(cd1.name
                        ORDER BY cp.level SEPARATOR '  >  ') AS name,
           c1.parent_id,
           c1.sort_order
    FROM " . DB_PREFIX . "category_path cp
    LEFT JOIN " . DB_PREFIX . "category c1 ON (cp.category_id = c1.category_id)
    LEFT JOIN " . DB_PREFIX . "category c2 ON (cp.path_id = c2.category_id)
    LEFT JOIN " . DB_PREFIX . "category_description cd1 ON (cp.path_id = cd1.category_id)
    LEFT JOIN " . DB_PREFIX . "category_description cd2 ON (cp.category_id = cd2.category_id)
    WHERE cd1.language_id = '" . (int)$this->config->get('config_language_id') . "'
      AND cd2.language_id = '" . (int)$this->config->get('config_language_id') ."'";

在 MySQL 中，我添加了新列“show_menu”(它可以是 NULL 或 1)，现在我想更改我的查询，它将仅返回 show_menu = 1 中的类别

据我所知，我需要这样的东西:WHERE show_menu IS 1。也许任何人都可以帮忙把它放在哪里？因为我试过了，但没有运气......

Answer 1

使用 show_menu = 1 或 show_menu IS NOT NULL

您不能对空值使用“=”运算符。