回显来自 MySQL 查询的单个结果 - Echo a single result from MySQL query

Echo a single result from MySQL query

本文关键字：单个结果查询 MySQL | 更新日期: 2023-09-27

我有以下MySQL查询;

    SELECT *, @rownum := @rownum + 1 from
    (
    SELECT (display_name) 'Author',
        IFNULL(ROUND(SUM(balance.meta_value),2),2) 'Balance'
    FROM posts p
    JOIN users u 
        ON p.post_author = u.ID
    JOIN postmeta odd ON p.ID = odd.post_id AND odd.meta_key = 'odd' AND odd.meta_value >= 1.5
    LEFT JOIN postmeta balance 
        ON p.ID = balance.post_id AND balance.meta_key = 'balance'
    WHERE p.post_status = 'publish' and p.post_author = 'User1' 
    GROUP BY u.ID
    ORDER BY Balance DESC
    )x, (SELECT @rownum := 0) r

生成下表;

 Users      Balance       @rownum := 0       @rownum := @rownum + 1
 User1      5.88              0               1
 User2      -23.41            0               2

如何回显第一个用户最后一列的值(其中 [@rownum ：= @rownum + 1] = 1。

谢谢

$result = mysql_query("your's sql query");
$row = mysql_fetch_array($result);
echo $row[2];

这是针对您的特定问题的代码。阅读更多关于这里的信息。整个扩展已被弃用，因此为了您的家庭作业，请阅读此内容并重写我的代码。

您需要使用 php 中的 mysqli_* 函数来连接和执行查询。执行查询后，检索第一行，然后回显第三列。

这样的事情应该可以工作(将 mysql 参数更改为主机的有效用户名/名称密码(：

<?php
$mysqli = new mysqli("localhost", "my_user", "my_password", "world");
/* check connection */
if (mysqli_connect_errno()) {
    printf("Connect failed: %s'n", mysqli_connect_error());
    exit();
}
$query = "SELECT *, @rownum := @rownum + 1 from
    (
    SELECT (display_name) 'Author',
        IFNULL(ROUND(SUM(balance.meta_value),2),2) 'Balance'
    FROM posts p
    JOIN users u 
        ON p.post_author = u.ID
    JOIN postmeta odd ON p.ID = odd.post_id AND odd.meta_key = 'odd' AND odd.meta_value >= 1.5
    LEFT JOIN postmeta balance 
        ON p.ID = balance.post_id AND balance.meta_key = 'balance'
    WHERE p.post_status = 'publish' and p.post_author = 'User1' 
    GROUP BY u.ID
    ORDER BY Balance DESC
    )x, (SELECT @rownum := 0) r";
if ($result = $mysqli->query($query)) {
    /* fetch object array */
    $row = $result->fetch_row(); // Fetch the first row
    echo $row[2]; // Print the 3rd column
    /* free result set */
    $result->close();
}
/* close connection */
$mysqli->close();
?>