从两个不同的数据库查询中找到两个计数列之间的差异，并在PHP中显示结果

Question

I asked a question last week and had assumed that the final part of it would be the straight forward part. However that is not proving to be the case. Here is a link to the original question and background.

I have two databases so have done 2 SQL queries and have merged the results into a table with four columns that displays

Name | Number| db1 Count | db2 Count |

That displays all the information perfectly. However, I need to get it to display, in a 5th column, the difference between db1 Count and db2 Count. This is the code I have:

$results = array();
while($row = $result1->fetch_assoc()) {
 //Adding all the 1st query results 
    $results[$row['number']] = $row;
}

while($row = $result2->fetch_assoc()) {
    if(! isset($results[$row['number']]) {
          $results[$row['number']] = $row;
    }else {
      $results[$row['number']]['db2 Count'] = $row['db2 Count'];
    }         
}
$db1_count = $row['db1 Count'];
$db2_count = $row['db2 Count'];
$difference = ($db1_count - $db2_count);


if ($results) {
    echo"<TABLE><caption>Total Call Count Overview</caption><TR>
      <TH>Number</TH>
      <TH>Company</TH>
      <TH>db1 Count</TH>
      <TH>db2 Count</TH>
      <TH>Difference</TH></TR>";

    foreach($results as $row) {
         echo"<TR><TD>". $row["number"]. "</TD>";
         echo"<TD>". $row["company"]. "</TD>";
         echo"<TD>". $row["db1 Count"]. "</TD>";
         echo"<TD>". $row["db2 Count"]. "</TD>";
         echo"<TD>". $difference . "</TD></TR>";
    }
    echo"</TABLE>";
 } else {
 echo"0 Results";
}

I had thought that putting the counts as variables

$db1_count = $row['db1 Count'];
$db2_count = $row['db2 Count'];
$difference = ($db1_count - $db2_count);

Would allow me to subtract them and echo the $difference variable, but I am just getting a column filled with zeros. I have also tried

echo"<TD>". $row['db1 Count'] - $row['db2 Count']. "</TD>";

But only to get the all the db2 Count figures across the top of the page.

Is there something I am missing, because I have tried answers to similar questions online but to no avail. I'm really quite new to this so any tips in the right direction would be much appreciated.

Answer 1

Move these lines:

$db1_count = $row['db1 Count'];
$db2_count = $row['db2 Count'];
$difference = ($db1_count - $db2_count);

inside the : foreach($results as $row)

so

foreach($results as $row) {
    $db1_count = $row['db1 Count'];
    $db2_count = $row['db2 Count'];
    $difference = ($db1_count - $db2_count);
    echo"<TR><TD>". $row["number"]. "</TD>";
    echo"<TD>". $row["company"]. "</TD>";
    echo"<TD>". $row["db1 Count"]. "</TD>";
    echo"<TD>". $row["db2 Count"]. "</TD>";
    echo"<TD>". $difference . "</TD></TR>";
}