Question

$sql = "SELECT # FROM users WHERE onduty = 1 AND loc_id = '{$site}';"; 
$result = mysql_query($sql);

I simply want to test if this is true or false. If it returns 0 rows, I want next line to be something like:

if (!$result) { //do this; }

However, in my test, I am getting false when I know it should be true. Is this sound logic here?

(note, yes I know I should be using mysqli_query, that is not what I am asking here)**

ANSWER:
This is what I used:

$login_state = false;
if(mysql_num_rows(mysql_query("SELECT 1 FROM users WHERE onduty = 1 AND loc_id = '{$site}';"))) {
    $login_state = true;
}

Answer 1

Use EXISTS:

SELECT EXISTS (SELECT 1 FROM users WHERE onduty = 1 AND loc_id = '{$site}') AS test;

Your original query would return "no row" if no row is found that matches the criteria. This one returns TRUE (1) or FALSE (0) every time.

In cases where there can be multiple rows matching the criteria and you are only interested whether at least one rows exists, performance of EXISTS is superior to a plain query. It can stop as soon as the first row is found and only returns 0 or 1.

db<>fiddle here
_{Old sqlfiddle}