serial is purely a shorthand way to create an
integer column with an associated sequence for its default values.
The documentation for
serial linked from the question even says as much:
The data types smallserial, serial and bigserial are not true types, but merely a notational convenience for creating unique identifier columns (similar to the AUTO_INCREMENT property supported by some other databases). In the current implementation, specifying:
CREATE TABLE tablename ( colname SERIAL );
is equivalent to specifying:
CREATE SEQUENCE tablename_colname_seq; CREATE TABLE tablename ( colname integer NOT NULL DEFAULT nextval('tablename_colname_seq') ); ALTER SEQUENCE tablename_colname_seq OWNED BY tablename.colname;