任何資料型別的列都可以包含 NULL
SELECT 1 NUM_COLUMN, 'foo' VARCHAR2_COLUMN from DUAL
UNION ALL
SELECT NULL, NULL from DUAL;
NUM_COLUMN | VARCHAR2_COLUMN |
---|---|
1 |
FOO |
(空值) | (空值) |
SELECT 1 NUM_COLUMN, 'foo' VARCHAR2_COLUMN from DUAL
UNION ALL
SELECT NULL, NULL from DUAL;
NUM_COLUMN | VARCHAR2_COLUMN |
---|---|
1 |
FOO |
(空值) | (空值) |