Question

我正在尝试获取特定项目的评论数量。

$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();

?>

$numLikes工作正常，但$numComments似乎返回NULL（来自var_dump），我不知道为什么。 phpMyAdmin中的SQL工作正常并返回注释数...

Answer 1

您可能希望在第一次查询时更改此内容

... AND r_value=3 OR r_value=2

到

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

或者这个

... AND r_value IN (2,3)

但是对于第二个查询，尝试一些简单的调试

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

然后

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

MySQL SELECT COUNT返回NULL

1 个答案: