The SE_Dissolve() function is an aggregate
function that computes the union of geometries of the same dimension.
If just one geometry satisfies your query, it is returned unaltered.
Syntax
SE_Dissolve (g1 ST_Geometry)
Usage
The following figure shows the union of various geometric
objects. Figure 1: Geometries
resulting from use of SE_Dissolve()
Return type
ST_Geometry
Example
The following
example creates a single multipolygon from the individual hexagons
that are inserted into the honeycomb table: