Re: SQL Newbie

> Data in speed history looks like this:
>     interface_id  updated_time          speed
>     1             2005-08-11 08:10:23   450112
>     1             2005-08-11 10:53:34   501120 <---
>     1             2005-08-11 10:58:11   450112
>     2             2005-08-11 08:10:23   450112 <---
>     2             2005-08-11 11:00:44   350234
>     3             2005-08-11 08:10:23   450112 <---
> The rows of speed_history I want back are marked above with ' <--- '.
> 
> Query results should look like:
>      interface.interface_id
>      interface.link_description
>      speed_history.updated_time
>      speed_history.speed

The main idea is to join a select of max speeds grouped by interface_id
to the interface table.

If the query runs too slow, then you may get better performance having an
index on (interface_id, speed) and using subselects. In this case
you want to select information about all of interfaces and then have
one of the columns be a subselect that selects one (using limit) speed
from rows that have a matching interface_id ordered by interface_id desc,
speed desc. This combination of limit and order by will be faster than
using max.