The following code creates a table without raising any errors:

CREATE TABLE test(
ID INTEGER NULL,
CONSTRAINT PK_test PRIMARY KEY(ID)
)

Note that I cannot insert a NULL, as expected:

INSERT INTO test
VALUES(1),(NULL)
ERROR:  null value in column "id" violates not-null constraint
DETAIL:  Failing row contains (null).
********** Error **********

ERROR: null value in column "id" violates not-null constraint
SQL state: 23502
Detail: Failing row contains (null).

Why can I create a table with a self-contradictory definition? ID column is explicitly declared as NULLable, and it is implicitly not nullable, as a part of the PRIMARY KEY. Does it make sense?

Edit: would it not be better if this self-contradictory CREATE TABLE just failed right there?