Accessing SQL Aliases with PHP - php

Question

This code works to give me what I want in my phpMyAdmin server:
SET #row_number = 0;
SELECT salesperson, units, profit, (#row_number:=#row_number + 1) AS position
FROM sales AS t ORDER BY profit DESC;
The problem happens when I transfer this to php:
<?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>";
}
It outputs the first three rows but not the fourth. The alias created with SQL.

Answer 1

First of all, you choose not exactly the best way to debug your output. Stringifying $row['position'] directly (by piping it into echo) hides a lot of useful info that you would be able to find otherwise.
Second, the query in your second snippet misses actually setting up that variable, like this:
$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

Additionally, in the latest version of MySQL (8.0+) window functions are finally supported which avoids the use of # session variables. Doing so you can also add row numbers by group with PARTITION BY clause:
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