php - 计算行数，仅当准备好的 PDO 多于 0 行时才执行 while 循环

Question

我正在尝试使用准备好的 PDO 语句执行 while 循环，但我只希望它在有任何行时执行。目前我正在使用它，但它似乎缺少第一个结果，大概是因为它移动了指针。

正确的做法是什么？

$stmt = $pdo->prepare('SELECT * FROM products p 
INNER JOIN products_to_categories c 
ON p.products_id = c.products_id
WHERE c.categories_id = ? 
AND products_status=? 
ORDER BY p.products_sort_order,p.products_name');
$stmt->execute([$categories_id,1]);
if(($category_row = $stmt->fetch(PDO::FETCH_ASSOC)) != null) { 
    $no_results = count($stmt->fetch(PDO::FETCH_ASSOC));
    while ($products_row = $stmt->fetch(PDO::FETCH_ASSOC)) {
    // show row info
    }
}

Answer 1

比如:

$stmt = $pdo->prepare('SELECT * FROM products p INNER JOIN products_to_categories c ON p.products_id = c.products_id
    WHERE c.categories_id = ? AND products_status=? ORDER BY p.products_sort_order,p.products_name');
$stmt->execute([$categories_id,1]);
$products_row="some_random_string";
while ($products_row = $stmt->fetch(PDO::FETCH_ASSOC) && $product_row!="some_random_string" && $product_row!=false) {
    // show row info
}

既然你谈到了行数，

$result = $con->prepare("SELECT count(*) FROM `products`"); 
$result->execute(); 
$number_of_rows = $result->fetchColumn();