I’ve been using explain to see what indices are being used. It took me a while to get my head around the results displayed by explain, but it is very useful information.

mysql_fetch_array is a superset of mysql_fetch_assoc, according the PHP manual. For that reason, I’d gone with mysql_fetch_array over mysql_fetch_assoc.

Interestingly, I just found this comment that suggests that there is a significant performance difference between mysql_fetch_assoc and mysql_fetch_array. I might have to rewrite some of my mysql_fetch_array calls. It’s not worth it for most pages, but I do have some pages where several hundred rows are retrieved, and the difference there could be worth it.

Anyway, both mysql_fetch_assoc and mysql_fetch_array are going to be far better than using my old friend mysql_result

I did once find a colleague’s statement with a subquery, where the subquery was checking about 5000 rows, and the main query was checking about 20,000 rows. A quick rewrite with a correct join and some decent indexes and I got it down to checking less than 100 rows (and that query was called on every page, eek).

I always use while ($rsArray = mysql_fetch_array($qidQuery)) to loop through the result set, but i’ve never thought of mysql_num_rows as inefficient…

Ian

Often you just need to process all the results of a query, without having to know beforehand how many rows you have. In that case, the mysql_num_rows is pointless, as mysql_fetch_array will automatically return false when there are no more results. I suspect that even with a counter, it’s less overhead than asking MySQL for the number of rows, with all the associated communication overhead, unless your results set is very large.

Using mysql_result does a seek within a results set for every single field and row. And there’s lots of communcations overhead. Whereas with mysql_fetch_array, it’s just one row after another, with no need to jump back and forward in the results set.

The MySQL manual recommends avoiding mysql_result in favour of the row based alternatives (such mysql_fetch_array). I’ve also read similar recommendations elsewhere.

http://uk2.php.net/function.mysql-result

I’m using mysql_fetch_array, because I much prefer working with named fields, rather than numbered fields.

I haven’t done any detailed tests, but things seem to be running significantly more quickly, although having made quite a few changes, it’s difficult to be specific about which ones made the most difference. I suspect the change from mysql_result to mysql_fetch_array was more than important than removing a mysql_num_results calls.

Interesting! - Are you saying that a while loop on mysql_fetch_array with a counter in the middle is faster than mysql_num_rows?

I’m very surprised by that…

Did you read that somewhere or just test it?

Ian