[postgis-users] ST_Boundary of some linestrings

[Nicolas Ribot]

> lisek lichu wrote:
>>
>> Hello,
>>
>> I hane in my database 6 linestrings and I want to get the boundary
>> rectangle from them (not from each of them)
>>
>> If i use:
>> select AsText(ST_Boundary(the_geom)) from segments;
>>
>> i get
>>
>> MULTIPOINT(-8.593025208 41.180818082,-8.594827652 41.187632944)
>> MULTIPOINT(-8.594827652 41.187632944,-8.591823578 41.193090782)
>> MULTIPOINT(-8.591823578 41.193090782,-8.611950874 41.190119708)
>> MULTIPOINT(-8.611950874 41.190119708,-8.613796234 41.179203081)
>> MULTIPOINT(-8.613796234 41.179203081,-8.602809906 41.180559684)
>> MULTIPOINT(-8.602809906 41.180559684,-8.593025208 41.180818082)
>>
>>
>> but i need one big Boundary. (should I group them by some atribute or
>> there is some siplier way to do that?)
>
> select AsText(ST_Envelope(ST_Collect(the_geom))) from segments;
>
> Does this work for you?
>

What about aggregate function st_extent ?

select asText(st_extent(the_geom)) from segments;

Nicolas