say I have this
$result = mysql_query(\'SELECT views FROM post ORDER BY views ASC\');
and I want to use the value at index 30 I assumed I
Your first example would actually do what you want, but be very expensive. The second is selecting the entire table, moving to the 30th row of the result, and then looping through all the results from then onwards.
You should instead do the following, which will only return one row and be a lot faster:
$result = mysql_query('SELECT views FROM post ORDER BY views ASC LIMIT 30,1');
Note that Soviut's explanation of LIMIT is not quite correct - it's (offset, number of rows) rather than (min, max).