>I would try
>SELECT st_envelope( st_collect(geom) ) FROM roads;
>HTH, Filip
>> I want to get the extensions of spatial table. Say that there is a spatial table named 'roads', and a some road geometry inside. I want to fetch the bounding box (envelope or extension) for that table, that means for all the roads that it has.
>>
>> According the OGC specification, this should be defined in the "geometry_columns" table. As four columns, "minX", "minY", "maxX" and "maxY". But I couldn't find it anywhere on my postgis. Yet.
>>
>> From which table/view? With what SQL?