How can I count the numbers of rows that a MySQL query returned?

Question

How can I count the number of rows that a MySQL query returned?

Answer 1

If you're fetching data using Wordpress, then you can access the number of rows returned using $wpdb->num_rows:

$wpdb->get_results( $wpdb->prepare('select * from mytable where foo = %s', $searchstring));
echo $wpdb->num_rows;

If you want a specific count based on a mysql count query then you do this:

$numrows = $wpdb->get_var($wpdb->prepare('SELECT COUNT(*) FROM mytable where foo = %s', $searchstring );
echo $numrows;

If you're running updates or deletes then the count of rows affected is returned directly from the function call:

$numrowsaffected = $wpdb->query($wpdb->prepare(
   'update mytable set val=%s where myid = %d', $valuetoupdate, $myid));

This applies also to $wpdb->update and $wpdb->delete.