php - Why you should not use mysql_fetch_assoc more than 1 time?

Question

Some people say you should not use mysql_fetch_assoc more than one time, why is that?

e.g.: I want to display two tables one with users who paid for membership, other with users who did not, so instead of querying database 2 times I query it one time and get $result variable with both types of users then I run loop mysql_fetch_assoc and see if list['membership'] = 'paid' then echo ...

Second time I loop loop mysql_fetch_assoc and see if list['membership'] = 'free' then echo ...

What uses less resources considering I got about equal amount of users who registered and unregistered.

Answer 1

Think of your query result set as a sausage, and mysql_fetch_assoc() as a knife that slices off a piece of that sausage. Every time you fetch a row, another piece of sausage is cut off, and it's always a NEW piece of sausage. You can't go and cut off a previously cut piece, because it's been eaten already.