Using count(*) vs num_rows

Question

To get number of rows in result set there are two ways:

1. Is to use query to get count

   $query=\"Select count(*) as count from some_table where type=

Answer 1

count is much more efficient both performance wise and memory wise as you're not having to retrieve so much data from the database server. If you count by a single column such as a unique id then you can get it a little more efficient