nested while loop stops after first iteration PHP - php

Question

I'm fairly new to this so I am probably missing something very basic, but I am trying to write some PHP script. I want to normalize my main table of data, which is info on used cars, make, model, price, etc. So I have another table with all of the unique car manufacturers in, this stores the makeName with a unique id makeId In my script, I connect to the database, read in all of the data from the main table, run it as an SQL query, then store it as a variable. I do the same with the make table.
Then I try to run through a nested while loop to replace all of the strings in the main table in the Manufacturer column with the makeId from the make table so that I can link these two tables. It works for one iteration then stops, I've tried adding !==FALSE after the fetch_assoc in either and both while loops, but that gives me infinite loops I think. Here is my code...
<?php
include("conn.php");
$sqlAll= "SELECT * FROM carData";
$carDataResult = $conn->query($sqlAll);
if(!$carDataResult){
echo $conn->error;
die();
}
$sqlMake = "SELECT * FROM 000make";
$makeResult = $conn->query($sqlMake);
if(!$makeResult){
echo $conn->error;
die();
}
while ( $make =$makeResult-> fetch_assoc()){
$makeID = $make['makeId'];
$makeName = $make['makeName'];
while ($row = $carDataResult->fetch_assoc()){
$sqlUpdate="UPDATE carData SET Manufacturer = '$makeID'
WHERE Manufacturer='$makeName' AND Manufacturer IS NOT NULL";
$res = $conn->query($sqlUpdate);
if(!$res){
echo $conn->error;
die();
}
}
}
?>

Answer 1

About 10 mins after I posted the question, after staring at this all day, I realised that I didn't need a nested loop at all and wrote the code below, which is clunky but it solved the problem, but I like your solution better #TangentiallyPerpendicular...thanks for your help guys...
while ($make =$makeResult-> fetch_assoc()){
$makeID = $make['makeId'];
$makeName = $make['makeName'];
$sqlUpdate="UPDATE carData SET Manufacturer = '$makeID'
WHERE Manufacturer='$makeName' AND Manufacturer IS NOT NULL";
$res = $conn->query($sqlUpdate);
if(!$res){
echo $conn->error;
die();
}
}

Answer 2

As a general rule, reading a result set and looping through it to run successive queries is the wrong way to deal with this sort of problem. You can do it all in a single query:
update carData set `Manufacturer` = (select `makeId` from `000make` where 000make.makeName=carData.Manufacturer)
Your entire program becomes:
<?php
include("conn.php");
$sqlAll= "update carData set `Manufacturer` = (select `makeId` from `000make` where 000make.makeName=models.Manufacturer) ";
$carDataResult = $conn->query($sqlAll);
if(!$carDataResult){
echo $conn->error;
die();
} else {
echo "Update Successful"
}
As an aside, I'd create a new column (called, perhaps, makeId) in your carData table and insert the data there rather than overwriting the Manufacturer column. That way you retain the Manufacturer column if something goes wrong. You can drop that column later.