如何顯示mysql的平均值

Question

如何顯示mysql中列的平均值？

下面是我的代碼，我至今嘗試過：

<?php 
    if (isset($_GET["age"])); 
    $age = ($_GET["age"]); 
    include($_SERVER["DOCUMENT_ROOT"] . "/includes/config.php"); 

    // Input 
    $sql = "SELECT AVG(column_name) FROM table_name"; 

    // Check age 
    if ($age > 99 or $age < 5) { 
    echo ("We only store data of people between the age of 5 and 99."); 
    if (!mysqli_query($conn, $sql)) { 
     die('Error: ' . ((is_object($GLOBALS["___mysqli_ston"])) ? mysqli_error($GLOBALS["___mysqli_ston"]) : (($___mysqli_res = mysqli_connect_error()) ? $___mysqli_res : false))); 
    } 
    } 
    else { 
    echo ("We got it!"); 
    } 

    // Close connection 
    ((is_null($___mysqli_res = mysqli_close($conn))) ? false : $___mysqli_res); 

    die(); 
?> 

但如何準確定義與AVG結果的變量，最大的2位小數？

我想使用並顯示到另一個文件（所以我會包括這一個）。

我現在所擁有的

<?php 
if (isset($_GET["age"])); 
$age = ($_GET["age"]); 
include($_SERVER["DOCUMENT_ROOT"] . "/3/includes/config.php"); 
include($_SERVER["DOCUMENT_ROOT"] . "/3/includes/opendb.php"); 

// My own created code 
$sql = $conn->query("SELECT ROUND(AVG(price AS FLOAT), 2) FROM data WHERE age= '$age'"); 
$data = $sql->mysqli_fetch_assoc(); 
$avg_data = $data['price']; 
echo $avg_data; 

// This below is from an other post but don't know how it works and if it is good. 
$ratings = $conn->query("SELECT AVG(price) avg_rating FROM data form_id = '" . $age . "'"); 
$data2 = $ratings->mysqli_fetch_assoc(); 
$avg_rating = $data2['avg_rating']; 
echo $avg_rating; 

die(); 

?> 

Answer 1

我如何固定它：

<?php 

if (isset($_GET["age"])) { 
$age = ($_GET["age"]); 

include($_SERVER["DOCUMENT_ROOT"] . "/3/includes/config.php"); 

$con=mysqli_connect($dbhost,$dbuser,$dbpass,$dbname); 

if (mysqli_connect_errno($con)) { 
    echo "Failed to connect to MySQL: " . mysqli_connect_error(); 
} 

$result = mysqli_query($con,"SELECT AVG(price) FROM data WHERE age= '$age'") or die("Error: " . mysqli_error($con)); 

while($row = mysqli_fetch_array($result)) { 
    echo $row['AVG(price)']; 
    echo number_format($row['AVG(price)'], 2); 
} 

die(); 
} 
else { 
echo 'Something went wrong, try again.'; 
} 

?> 

Answer 2

使用像這樣來平均witth兩個小數點。

$sql = "SELECT ROUND(AVG(column_name AS FLOAT), 2) FROM table_name"; 

Answer 3

$sql = 'SELECT *, ROUND(AVG(column_name), 2) AS avg_value FROM table_name'; 

avg_value將存儲四捨五入+平均值，並添加*如果需要獲得所有的列。