多项选择题
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.
多项选择题 Evaluate the SQL statement: TRUNCATE TABLE DEPT; Which three are true about the SQL statement? （）
单项选择题 You need to design a student registration database that contains several tables storing academic information. The STUDENTS table stores information about a student. The STUDENT_GRADES table stores information about the students grades. Both of the tables have a column named STUDENT_ID. The STUDENT_ID column in the STUDENTS table is a primary key. You need to create a foreign key on the STUDENT_ID column of the STUDENT_GRADES table that points to the STUDENT_ID column of the STUDENTS table. Which statement creates the foreign key?（）
多项选择题 Which two statements about subqueries are true? （）