MySQL SELECT COUNT返回NULL

Question

我正在嘗試獲取特定項目的評論數。

$stmt1 = $conn->prepare("SELECT COUNT(r_value) FROM ratings WHERE r_snippet=? AND r_value=3 OR r_value=2");
$stmt2 = $conn->prepare("SELECT COUNT(c_id) FROM comments WHERE c_snippet=?");

foreach ($snippets as $snippet){

    $s_id = $snippet['s_id'];
    $s_thumb = $snippet['s_thumb'];

    $stmt1->bind_param("i",$s_id);
    $stmt1->execute();
    $stmt1->bind_result($numLikes);
    $stmt1->fetch();

    $stmt2->bind_param("i",$s_id);
    $stmt2->execute();
    $stmt2->bind_result($numComments);
    $stmt2->fetch();

?>

    ** HTML here **    

<?php 

}

$stmt1->close();
$stmt2->close();

?>

$numLikes正常工作，但$numComments似乎返回NULL（從var_dump ），我不確定為什么。 phpMyAdmin中的SQL可以正常工作並返回注釋數...

Answer 1

您可能想在第一個查詢中更改此設置

... AND r_value=3 OR r_value=2

至

... AND (r_value=3 OR r_value=2)

或這個

... AND r_value IN (2,3)

---

但是對於第二個查詢，請嘗試一些簡單的調試操作

$stmt2 = $conn->prepare("SELECT * FROM comments WHERE c_snippet=10");

然后

$stmt2 = $conn->prepare("SELECT count(*) FROM comments WHERE c_snippet=10");