SQL: Union of polygons

Question

I have a table with a single column of geometry type, containing polygons. How do I get the union of all the polygons in the table?

Answer 1

you mean, if you have 2 squares, lets say

(0 0 , 1 0 , 0 1 , 1 1) 

and

(1 0 , 1 1 , 2 0 , 2 1)

you end up with a rectangle:

(0 0, 2 0 ,0 1, 2 1)

if yes, try the GPC (General Polygon Clipper library)

This link may also help you