mysql_num_rows() return 0 when using AND

Question

I am trying to retrieve the number of rows based on this query in wordpress:

protected function wp_has_facility($fid)
{
    //global $wpdb;

    $fid = intval($fid);

    $sql = "SELECT post_id FROM wprf_postmeta WHERE meta_value = '".$fid."' AND meta_key = 'facility_id'";
    $result = mysql_query($sql) or die(mysql_error());

    $num_rows = mysql_num_rows($result);

    echo $num_rows;

    return $num_rows;
}

$num_rows returns 0 when this function is ran.

If I echo the query string and run it in phpmyadmin, it selects successfully giving me a number of rows.

After further investigation it looks like when I hardcode the meta_value it will give me a row count. But if I'm populating the string with variables it doesn't work.

Any ideas?

Have you got any entries with meta_key "thing_id" actually, or was it just a placeholder for a var, i.e. $thing_id? — moonwave99
– moonwave99, Commented Sep 4, 2012 at 17:41
Are you sure that there are datasets which met both conditions? Beside that, try out the query in PHPMyAdmin. — ComFreek
– ComFreek, Commented Sep 4, 2012 at 17:41
A query can be successful and return 0 rows. Obviously, your AND condition limits the query to 0 rows...i.e, nothing matches the meta_key you are passing it. Try running your queries directly w/ phpMyAdmin or MySQL Workbench to verify. — Jeremy Harris
– Jeremy Harris, Commented Sep 4, 2012 at 17:41
What is thing_id? Did you mean this: $result = mysql_query( "SELECT * FROM wprf_postmeta WHERE meta_value = 123 AND meta_key = '$thing_id'") or die(mysql_error()); $num_things = mysql_num_rows($result); — JvdBerg
– JvdBerg, Commented Sep 4, 2012 at 17:45
I'm sorry I should have mentioned - I did try it in phpmyadmin with the AND statement and it does return rows, along with a row count. However in PHP it does not — Phill Tidd
– Phill Tidd, Commented Sep 4, 2012 at 17:50

Community · Accepted Answer · 2020-06-20 09:12:55Z

8

This only means your table currently contains no record that satisfies both criteria.

Remarks about your code:

Concatenation is not necessary, you may replace the query with:

$sql = "SELECT post_id FROM wprf_postmeta WHERE meta_value = '$fid' AND meta_key = 'facility_id'";

mysql_* functions are deprecated, you should avoid using them as they will be removed in a future version of PHP. Here are the alternatives.

edited Jun 20, 2020 at 9:12

CommunityBot

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answered Sep 4, 2012 at 17:43

Jocelyn

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7 Comments

Phill Tidd Over a year ago

The same query in phpmyadmin gave me matching records

Phill Tidd Over a year ago

I copied and pasted the full query string from my PHP script into phpmyadmin. PHP giving me num_rows of 0, phpmyadmin giving me 1.

András Váczi Over a year ago

@PhillTidd Please copy and paste it here as well. Try to echo the SQL string, not rownum.

Phill Tidd Over a year ago

@dezso SELECT post_id FROM wprf_postmeta WHERE meta_value = '21' AND meta_key = 'facility_id'

András Váczi Over a year ago

@PhillTidd are you sure that $fid does not contain a space or something? And a sidenote: does meta_value contain numeric values? What is its type? Is it different from wp_postmeta?

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