Hi Li Li,
In general it is best practice to keep your tables homogeneous with
respect to type of geometry. The reason for this is that many PostGIS
function expect to operate on a specific type of geometry. Also a column
in ralational databases is typically strongly typed, ie you do not
normally expect to find character data in numeric columns, etc.
If you want to mix data in the geometry column then you can just drop
the constraints on that table after you create it, but I do not think
this is recommended. Or you can create it by hand like:
create table blahblah (
gid serial,
...
the_geom geometry);
and this table has no constraints on it and you can load any geometries
into it.
-Steve
Li Li wrote:
How to let the table allow both polygon and multipolygon?
I create geometry column use SELECT AddGeometryColumn
('','china_block','geom',4326,'POLYGON',2);
I tried SELECT AddGeometryColumn ('','mytable','geom',4326,'MULTIPOLYGON',2);
it says
ERROR: column "geom" of relation "china_block" already exists
CONTEXT: SQL statement "ALTER TABLE public.china_block ADD COLUMN
geom geometry "
PL/pgSQL function "addgeometrycolumn" line 121 at EXECUTE statement
SQL statement "SELECT AddGeometryColumn('', $1 , $2 , $3 , $4 , $5 , $6 )"
PL/pgSQL function "addgeometrycolumn" line 4 at SQL statement
As you suggested, I can change POLYGON to MULTIPOLYGON.
But if the column has LINESTRING and POLYGON, what should I do?
thanks.
2010/4/13 Stephen Woodbridge <[email protected]>:
Li Li wrote:
I have a table from oracle. a spatial column geom is SDO_GEOMETRY. I
migrated it to postgis. this geom column has record with type of
POLYGON and MULTIPOLYGON. is there any common type that can store any
geometry?
The common type in PostGIS is "geometry", but you can also change the
constraints you table to allow both POLYGON and MULTIPOLYGON.
Or you can do something like:
update mytable set the_geom = ST_Multi(the_geom)
where ST_GeometryType = "POLYGON';
-Steve W
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