166. View the Exhibit and examine the structures of the EMPLOYEES and DEPARTMENTS tables.
You want to update the EMPLOYEES table as follows:4 ? 4;
-Update only those employees who work in Boston or Seattle (locations 2900 and 2700).
-Set department_id for these employees to the department_id corresponding to London (location_id
2100).
-Set the employees' salary in location_id 2100 to 1.1 times the average salary of their department.
-Set the employees' commission in location_id 2100 to 1.5 times the average commission of their
department.
You issue the following command:
SQL>UPDATE employees
SET department_id =
(SELECT department_id
FROM departments
WHERE location_id = 2100),
(salary, commission) =
(SELECT 1.1*AVG(salary), 1.5*AVG(commission)
FROM employees, departments
WHERE departments.location_id IN(2900,2700,2100))
WHERE department_id IN
(SELECT department_id
FROM departments
WHERE location_id = 2900
OR location_id = 2700)
What is the outcome?
A. It executes successfully and gives the correct result.
B. It executes successfully but does not give the correct result.
C. It generates an error because a subquery cannot have a join condition in an UPDATE statement.
D. It generates an error because multiple columns (SALARY, COMMISION) cannot be specified together
in an UPDATE statement.
Answer: B
答案解析：
题意要求更新条件：
1.只更新那些在Boston或Seattle工作的employees（locations为2900或者2700）
2.设置这些employees的department_id为London（location_id 2100）对应的department_id
3.设置location_id 2100的employees' salary为他们部门的平均薪水的1.1倍
4.设置location_id 2100的employees' commission为他们部门的平均提成的1.5倍
UPDATE employees
SET department_id =
(SELECT department_id FROM departments WHERE location_id = 2100),
(salary, commission) = (SELECT 1.1*AVG(salary), 1.5*AVG(commission) FROM employees, departments
WHERE departments.location_id IN(2900,2700,2100))
WHERE department_id IN (SELECT department_id FROM departments WHERE location_id = 2900 OR location_id = 2700)