How can I improve this PHP MySQL call? - php

Question

I'm trying to update an older MySQL PHP method call but I end up calling the same SELECT call twice to achieve the same result. Is there a better way to do this?
Here is the original:
function updateProbabilities()
{
// first update the word count of each category
$rs = $this->con->select("SELECT category_id, SUM(count) AS total FROM nb_wordfreqs WHERE 1 GROUP BY category_id");
$total_words = 0;
while (!$rs->EOF()) {
$total_words += $rs->f('total');
$rs->moveNext();
}
$rs->moveStart();
if ($total_words == 0) {
$this->con->execute("UPDATE nb_categories SET word_count=0, probability=0 WHERE 1");
return true;
}
while (!$rs->EOF()) {
$proba = $rs->f('total')/$total_words;
$this->con->execute("UPDATE nb_categories SET word_count=".(int)$rs->f('total').",
probability=".$proba."
WHERE category_id = '".$rs->f('category_id')."'");
$rs->moveNext();
}
return true;
}
Here is my version:
function updateProbabilities() {
$sql = "SELECT category_id, SUM(count) AS total FROM nb_wordfreqs WHERE 1 GROUP BY category_id";
$res = mysql_query($sql) or die (mysql_error());
$total_words = 0;
while ($row = mysql_fetch_array($res, MYSQL_ASSOC)) {
$total_words += $row['total'];
}
if ($total_words >= 1) {
$sql = "SELECT category_id, SUM(count) AS total FROM nb_wordfreqs WHERE 1 GROUP BY category_id";
$res = mysql_query($sql) or die (mysql_error());
while ($row = mysql_fetch_array($res, MYSQL_ASSOC)) {
$proba = $row['total']/$total_words;
$count = (int)$row['total'];
$sql = "UPDATE nb_categories SET word_count=".$count.",
probability=".$proba."
WHERE category_id = '".$row['category_id']."'";
mysql_query($sql) or die (mysql_error());
}
}
else {
$sql = "UPDATE nb_categories SET word_count=0, probability=0 WHERE 1";
mysql_query($sql) or die (mysql_error());
}
return true;
}
Do you see any way I can avoid this second duplicate SELECT call?

Answer 1

The first time you run the query, add this to the while loop to store the results:
$rowarray[] = $row; // added to prevent running it twice
Then the second time it comes up, replace this:
$sql = "SELECT category_id, SUM(count) AS total FROM nb_wordfreqs WHERE 1 GROUP BY category_id";
$res = mysql_query($sql) or die (mysql_error());
while ($row = mysql_fetch_array($res, MYSQL_ASSOC)) {
with this:
foreach ($rowarray as $row) {
ALSO: move away from mysql_ functions, as they are deprecated and will soon be removed from PHP. Change to a PDO or MySQLi. You're already upating the code, may as well make that change too.

Answer 2

The mysql equivalent of $rs->moveStart() is:
mysql_data_seek($res, 0);
P.S. If you're rewriting into a new API, why are you using the deprecated mysql extension? You should use mysqli or PDO? They have similar methods for rewinding the cursor.

Answer 3

You can set the first query to a unique variable, and re-use the results of that query.
function updateProbabilities() {
$sql = "SELECT category_id, SUM(count) AS total FROM nb_wordfreqs WHERE 1 GROUP BY category_id";
$res = mysql_query($sql) or die (mysql_error());
$total_words = 0;
$results = array();
while ($row1 = mysql_fetch_array($res, MYSQL_ASSOC)) {
$total_words += $row1['total'];
$results[] = $row1;
}
if ($total_words >= 1) {
foreach ($results as $row2) {
$proba = $row2['total']/$total_words;
$count = (int)$row2['total'];
$sql = "UPDATE nb_categories SET word_count=".$count.",
probability=".$proba."
WHERE category_id = '".$row2['category_id']."'";
mysql_query($sql) or die (mysql_error());
}
}
else {
$sql = "UPDATE nb_categories SET word_count=0, probability=0 WHERE 1";
mysql_query($sql) or die (mysql_error());
}
return true;
}