Reading data from table (performance test)

I just came to the conclusion that this method:

$n = mysql_num_rows
for($i=0;$i<$n;$i++)
{
    mysql_data_seek($query,$i);
    manipulate row's data
}

Code (markup):

is more or less 2,5x times faster than:

while($dat = mysql_fetch)
    manipulate row's data

Code (markup):

The second is much easier to write but the performance is terrible, can you please confirm if i'm right?.

 

    mysql_data_seek($query,$i);

PHP:

Doesn't actually return any data, it just sets the point to the specified row (per se.)

You still need to run mysql_fetch_assoc (or w/e) afterwards, it's faster to just use mysql_fetch_assoc in the first place.

 

The "manipulate row's data" includes the fetch +_+

I was just trying to figure out why the while is so slow...

 

The while isn't/shouldn't be slow.