单项选择题

A. ALTER TABLE students ADD PRIMARY KEY _ id;B. ALTER T……

You need to modify the STUDENTS table to add a primary key on the STUDENT_ID column. The table is currently empty. Which statement accomplishes this task?（）

A. ALTER TABLE students ADD PRIMARY KEY _ id;
B. ALTER TABLE students ADD CONSTRAINT PRIMARY KEY (student_id);
C. ALTER TABLE students ADD CONSTRAINT stud_id_pk PRIMARY KEY student_id;
D. ALTER TABLE students ADD CONSTRAINT stud_id_pk PRIMARY KEY (student_id);
E. ALTER TABLE students MODIFY CONSTRAINT stud_id_pk PRIMARY KEY (student_id);

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单项选择题You are the DBA for an academic database. You need to create a role that allows a group of users to modify existing rows in the STUDENT_GRADES table. Which set of statements accomplishes this? （）

A. CREATE ROLL registrar; GRANT MODIFY ON student_grant TO registrar; GRANT registrar to user 1, user2, user3
B. CREATE NEW ROLE registrar; GRANT ALL ON student_grant TO registrar; GRANT registrar to user 1, user2, user3
C. CREATE ROLL registrar; GRANT UPDATE ON student_grant TO registrar; GRANT ROLE to user1, user2, user3
D. CREATE ROLL registrar; GRANT UPDATE ON student_grant TO registrar; GRANT registrar to user 1, user2, user3;
E. CREATE registrar; GRANT CHANGE ON student_grant TO registrar; GRANT registrar;

单项选择题Evaluate this SQL statement: SELECT ename, sal, 12* sal+100 FROM emp; The SAL column stores the monthly salary of the employee. Which change must be made to the above syntax to calculate the annual compensation as monthly salary plus a monthly bonus of $100, multiplied by 12 ? （）

A. No change is required to achieve the desired results.
B. SELECT ename, sal, 12* (sal+100) FROM emp;
C. SELECT ename, sal, (12* sal)+100 FROM emp;
D. SELECT ename, sal +100,*12 FROM emp;

单项选择题Which statement adds a constraint that ensures the CUSTOMER_NAME column of the CUSTOMERS table holds a value?（）

A. ALTER TABLE customers ADD CONSTRAINT cust_name_nn CHECK customer_name IS NOT NULL;
B. ALTER TABLE customers MODIFY CONSTRAINT cust_name_nn CHECK customer_name IS NOT NULL;
C. ALTER TABLE customers MODIFY customer_name CONSTRAINT cust_name_nn NOT NULL;
D. ALTER TABLE customers MODIFY customer_name CONSTRAINT cust_name_nn IS NOT NULL;
E. ALTER TABLE customers MODIFY name CONSTRAINT cust_name_nn NOT NULL;
F. ALTER TABLE customers ADD CONSTRAINT cust_name_nn CHECK customer_name NOT NULL;

单项选择题Examine the description of the EMPLOYEES table: EMP_ID NUMBER(4) NOT NULL LAST_NAME VARCHAR2(30) NOT NULL FIRST_NAME VARCHAR2(30) DEPT_ID NUMBER(2) Which statement produces the number of different departments that have employees with last name Smith? （）

A. SELECT COUNT (*) FROM employees WHERE last _name='smith';
B. SELECT COUNT (dept_id) FROM employees WHERE last _name='smith';
C. SELECT DISTINCT (COUNT (dept_id) FROM employees WHERE last _name='smith';
D. SELECT COUNT (DISTINCT dept_id) FROM employees WHERE last _name='smith';
E. SELECT UNIQE (dept_id) FROM employees WHERE last _name='smith';

单项选择题Which is an iSQL*Plus command? （）

A. INSERT
B. UPDATE
C. SELECT
D. DESCRIBE
E. DELETE
F. RENAME