CREATE TABLE T (A NUMBER, B NUMBER); ALTER TABLE T ADD CONSTRAINT UK UNIQUE (A, B); INSERT INTO t (a, b) VALUES (NULL, NULL); INSERT INTO t (a, b) VALUES (NULL, NULL); INSERT INTO t (a, b) VALUES (NULL, 1); INSERT INTO t (a, b) VALUES (NULL, 1); INSERT INTO t (a, b) VALUES (1, NULL); INSERT INTO t (a, b) VALUES (1, NULL); INSERT INTO t (a, b) VALUES (1, 1); INSERT INTO t (a, b) VALUES (1, 1); SELECT * FROM t; /
Tags: Oracle