使用 PHP 访问 SQL 个别名

Question

此代码可以在我的 phpMyAdmin 服务器中提供我想要的内容：

SET @row_number = 0;
SELECT salesperson, units, profit, (@row_number:=@row_number + 1) AS position
FROM sales AS t ORDER BY profit DESC;

当我将其传输到 php 时出现问题:

<?php 
    
$sql = "SELECT salesperson, units, profit, (@row_number:=@row_number + 1) AS position\n"
. "FROM sales AS t ORDER BY profit DESC";
$result = mysqli_query($conn, $sql); 
$resultCheck = mysqli_num_rows($result);
if ($resultCheck > 0){
    while ($row = mysqli_fetch_assoc($result)) 
        echo $row['salesperson'] . " " . $row['units'] . " " . $row['profit'] .$row['position'] . "<br>";
}

它输出前三行但不输出第四行。使用 SQL.

创建的别名

Answer 1

首先，您选择的调试输出的方式不完全是最佳方式。直接将 $row['position'] 字符串化（通过管道将其输入 echo）隐藏了很多您可以通过其他方式找到的有用信息。

其次，第二个代码段中的查询没有实际设置该变量，如下所示：

$sql = <<<QUERY
  SELECT salesperson, units, profit, 
         (@row_number:=@row_number + 1) AS position
  FROM sales AS t, (SELECT @row_number := 0) AS r
  ORDER BY profit DESC
QUERY;

$result = mysqli_query($conn, $sql); 
$resultCheck = mysqli_num_rows($result);
if ($resultCheck > 0){
  while ($row = mysqli_fetch_assoc($result)) {
    echo "$row[salesperson] $row[units] $row[profit] $row[position]<br>";
  }
}

Answer 2

此外，在最新版本MySQL (8.0+) 中终于支持window functions，避免使用@ 会话变量。这样做，您还可以使用 PARTITION BY 子句按组添加行号：

SELECT salesperson
       , units
       , profit
       , ROW_NUMBER() OVER(ORDER BY profit DESC) AS `overall_position`
       , ROW_NUMBER() OVER(PARTITION BY salesperson
                           ORDER BY profit DESC) AS `salesperson_position`
FROM sales
ORDER BY profit DESC

使用 PHP 访问 SQL 个别名

Accessing SQL Aliases with PHP

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sql

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