[postgis-users] query question group by envelope

[Jon Saints]

hi list

I am learning postgis sql sytax. I have a set of
polygons representing the islands of indonesia loaded
into a postgis table.  Each of the polygons has an
attribute which is the name of the province that the
island belongs.  

How can write a query to find the max envelope extent
of all islands for a given province?

Thanks in advance
Jon