Best way to check if mysql_query returned any results?

Question

I'm looking for the best way to check and see if any results were returned in a query. I feel like I write this part of code a lot and sometimes I get errors, and sometimes I don't.

For example, I run this query to check if a username exists before inserting a new one into the database.

$result = mysql_query("SELECT * FROM ..."); 

Then I want to check and see if any results were returned. Here is one way I do it:

if (!$result) { PERFORM ACTION } 

If the first way doesn't work, then sometimes this will:

if (mysql_num_rows($result)==0) { PERFORM ACTION } 

Then I even saw that I could do it this way the other day:

list($total) = mysql_fetch_row($result); if ($total==0) { PERFORM ACTION } 

What is the best way to do this?

Answer 1

if (mysql_num_rows($result)==0) { PERFORM ACTION } 

For PHP 5 and 7 and above use mysqli:

if (mysqli_num_rows($result)==0) { PERFORM ACTION } 

Answer 2

One way to do it is to check what mysql_num_rows returns. A minimal complete example would be the following:

if ($result = mysql_query($sql) && mysql_num_rows($result) > 0) {     // there are results in $result } else {     // no results } 

But it's recommended that you check the return value of mysql_query and handle it properly in the case it's false (which would be caused by an error); probably by also calling mysql_error and logging the error somewhere.