我想计算评级系统的平均值，但我在innodb中有一个普通表，在json中有一列名为"reviews"，结构如下：
{"comments":
[
{"name": "Jonh", "text": "nice phone", "star": 4},
{"name": "igon", "text": "not good", "star": 2},
{"name": "marco", "text": "i not like this", "star": 3},
{"name": "david", "text": "good product", "stelle": 5}
]
}
现在我需要计算平均恒星。它是在sql中还是在php中？在sql中，我不知道如何操作，在php中，我遇到了只提取全明星的查询问题，例如：
$reviews_nn = $rowprod["reviews"];
$reviews = json_decode($reviews_nn,true);
$max = 0;
$n = 0;
foreach ($reviews[comments][star] as $rate => $count) {
echo 'Seen ', $count, ' ratings of ', $rate, "'n";
$max += $rate * $count;
$n += $count;
}
echo 'Average rating: ', $max / $n, "'n";
但结果是NAN。。。不是整数吗？它是星形中的整数
星=4
not star="4"
我希望你能帮助我……坦克！！！
您的代码根本无法理解，但我为您创建了一个示例，我认为它将有助于解决您的问题：-
<?php
$data = '{"comments": [{"name": "Jonh", "text": "nice phone", "star": 4}, {"name": "igon", "text": "not good", "star": 2}, {"name": "marco", "text": "i not like this", "star": 3}, {"name": "david", "text": "good product", "stelle": 5}]}'; // your json data
//$reviews_nn = $rowprod["reviews"]; // i don't get from where you are getting this
$reviews = json_decode($data,true); // decode the json data
$max = 0;
$n = count($reviews['comments']); // get the count of comments
echo "<pre/>";print_r($reviews); // print json decoded data
foreach ($reviews['comments'] as $rate => $count) { // iterate through array
$max = $max+$count['star'];
}
echo 'Average rating: ', $max / $n, "'n";
?>
输出：-https://eval.in/545582
注意：-我已经获取了您的json数据，但更改了变量名。我希望它很容易理解我的代码中发生了什么。谢谢
$reviews_nn = $rowprod["reviews"];
$reviews = json_decode($reviews_nn,true);
$numberOfReviews = 0;
$totalStars = 0;
foreach($reviews['comments'] as $review)
{
$numberofReviews++;
$totalStars += $review['star'];
}
$average = $totalStars/$numberOfReviews;
echo 'Average rating: '.$average;
这应该行得通。