关系“ pk”已经存在于Postgresql 9.1中

Question

I am new to Postgres/PostGIS, currently following a PostGIS book. When I tried one of their example's query, I get the error below stating that the relation "pk" already exists . Does this mean that 2 tables cannot have constraints with the same names?

Query:

CREATE TABLE roads(gid serial PRIMARY KEY, road_name character varying(100));
SELECT AddGeometryColumn('public', 'roads', 'geom', 4269, 'LINESTRING',2);

CREATE TABLE roads_NE(CONSTRAINT pk PRIMARY KEY (gid))
INHERITS (roads);

ALTER TABLE roads_NE
ADD CONSTRAINT chk CHECK (state
IN ('MA', 'ME', 'NH', 'VT', 'CT', 'RI'));

CREATE TABLE roads_SW(CONSTRAINT pk PRIMARY KEY (gid))
INHERITS (roads);

ALTER TABLE roads_SW
ADD CONSTRAINT chk CHECK (state IN ('AZ', 'NM', 'NV'));

Error:

NOTICE:  CREATE TABLE / PRIMARY KEY will create implicit index "pk" for table "roads_sw"


ERROR:  relation "pk" already exists

********** Error **********

ERROR: relation "pk" already exists
SQL state: 42P07

Answer 1

Yes. You need to use a different name within a database