Retrieving COUNT of a calculated expression

I read here that I can include an argument inside COUNT, to return a calculated value. I'm trying the following but I'm missing something. Ca开发者_如何学JAVAn you help? Thanks!

  mysql_select_db(DATABASE_NAME, $connection);
    $client = "demo/";
    $result = mysql_query
    (
        "SELECT 
        COUNT(page_max > 126) AS completed 
        FROM " .SESSIONDB. " 
        WHERE client = '$client' 
        AND page = 'interaction.php'
        "
    ); 
    if(mysql_error()) die(DIRECTORY_TITLE . " - Error DBA110 " . mysql_error());
    // output THE QUERY
    while($row = mysql_fetch_assoc($result))
    {
        echo $row['completed'];
    }

Try

 "SELECT 
    COUNT(*) AS completed 
    FROM " .SESSIONDB. " 
    WHERE client = '$client' AND page_max > 126
    AND page = 'interaction.php'"

How about this

SELECT 
SUM(CASE WHEN page_max > 126 THEN 1 ELSE 0 END) AS completed 
FROM table
WHERE client = '$client' 
AND page = 'interaction.php'

Or as Nicolò Martini said, move page_max to WHERE condition if you don't need total count of items.

This should do what you want:

SELECT COUNT(IF(page_max>126,1,NULL)) AS completed ....

COUNT counts the number of rows that aren't NULL. This expression turns anything where page_max is greater than 126 into 1 and anything that isn't into NULL.

That said, why not just move page_max to the WHERE condition?