单项选择题
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 student_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);
相关考题
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多项选择题
Click the Exhibit button and examine the data from the EMP table. The COMMISSION column shows the monthly commission earned by the employee. Which three tasks would require subqueries or joins in order to be performed in a single step?（）
A.deleting the records of employees who do not earn commission
B.increasing the commission of employee 3 by the average commission earned in department 20
C.finding the number of employees who do NOT earn commission and are working for department 20
D.inserting into the table a new employee 10 who works for department 20 and earns a commission that is equal to the commission earned by employee 3
E.creating a table called COMMISSION that has the same structure and data as the columns EMP_ID and COMMISSION of the EMP table
F.decreasing the commission by 150 for the employees who are working in department 30 and earning a commission of more than 800 -
单项选择题
Evaluate this SQL statement: SELECT e.EMPLOYEE_ID,e.LAST_NAME,e.DEPARTMENT_ID, d.DEPARTMENT_NAME FROM EMPLOYEES e, DEPARTMENTS d WHERE e.DEPARTMENT_ID = d.DEPARTMENT_ID; In the statement, which capabilities of a SELECT statement are performed?（）
A.selection, projection, join
B.difference, projection, join
C.selection, intersection, join
D.intersection, projection, join
E.difference, projection, product -
单项选择题
Click the Exhibit button and examine the data from the ORDERS and CUSTOMERS tables. Evaluate this SQL statement: SELECT cust_id, ord_total FROM orders WHERE ord_total > ANY(SELECT ord_total FROM orders WHERE cust_id IN (SELECT cust_id FROM customers WHERE city LIKENew York)); What is the result when the above query is executed?（）
A.A
B.B
C.C
D.D
E.E
