如何使这个MySQL Count查询更有效？

Question

//get the current member count
$sql = ("SELECT count(member_id) as total_members from exp_members");
$result = mysql_query($sql) or die(mysql_error());
$num_rows = mysql_num_rows($result);
if ($num_rows != 0) {
    while($row = mysql_fetch_array($result)) {
        $total_members = $row['total_members'];
    }
}

//get list of products
$sql = ("SELECT m_field_id, m_field_label from exp_member_fields where m_field_name like 'cf_member_ap_%' order by m_field_id asc");
$result = mysql_query($sql) or die(mysql_error());
$num_rows = mysql_num_rows($result);

if ($num_rows != 0) {

    while($row = mysql_fetch_array($result)) {

        $m_field_id             = $row['m_field_id'];
        $m_field_label          = $row['m_field_label'];

        $sql2 = ("SELECT count(m_field_id_".$m_field_id.") as count from exp_member_data where m_field_id_".$m_field_id." = 'y'");
        $result2 = mysql_query($sql2) or die(mysql_error());
        $num_rows2 = mysql_num_rows($result2);

        if ($num_rows2 != 0) {
            while($row2 = mysql_fetch_array($result2)) {
                $p = ($row2['count']/$total_members)*100;
                $n = $row2['count'];
                $out .= '<tr><td>'.$m_field_label.'</td><td>'.number_format($p,1).'%</td><td>'.$n.'</td></tr>';
            }
        }

    }


}

Answer 1

It's easier to help if you can describe in non-code terms what you're trying to accomplish. But one indicator of a problem is seeing a php loop on rows from one query with another query executing for each row.

There are ways to query for subtotals. But it would be easier to explain if you can explain the goal a bit.

Answer 2

count query would always return 1 row, so you don't need the loop

$sql = ("SELECT count(member_id) as total_members from exp_members");
$result = mysql_query($sql) or die(mysql_error());
$row = mysql_fetch_array($result);
$total_members = $row['total_members'];

Other than that i am not sure how you can make it better. You can do the same for both of your count queries.

As these are straight forward queries, any bottleneck i guess now would be on the MySQL end

Answer 3

The first COUNT query ("get the current member count") should execute almost instantaneously.

The second query ("get list of products") may be slow depending on your indexes. You are querying on m_field_name and then ordering on m_field_id so you may need a combined index of the two.

The third query, which is executed repeatedly (once for each product), is querying on m_field_id_* (ie any of a number of possible fields), so you should probably make sure they are indexed.

In summary, you need to a) figure out which query is running slow, b) index things that need to be indexed, and c) combine queries if possible.