试题详情
- 多项选择题Which two statements are true about constraints? （）
A、The UNIQUE constraint does not permit a null value for the column.
B、A UNIQUE index gets created for columns with PRIMARY KEY and UNIQUE constraints.
C、The PRIMARY KEY and FOREIGN KEY constraints create a UNIQUE index.
D、The NOT NULL constraint ensures that null values are not permitted for the column.
- B,D
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