web前端開發技術之SQL面試用題
SQL面試用題
- 查詢每個月倒數第 2 天入職的員工的資訊.
- 查詢出 last_name 為 ‘Chen’ 的 manager 的資訊.
- 查詢平均工資高於 8000 的部門 id 和它的平均工資.
- 查詢工資最低的員工資訊: last_name, salary
- 查詢平均工資最低的部門資訊
- 查詢平均工資最低的部門資訊和該部門的平均工資
- 查詢平均工資最高的 job 資訊
- 查詢平均工資高於公司平均工資的部門有哪些?
- 查詢出公司中所有 manager 的詳細資訊.
- 各個部門中 最高工資中最低的那個部門的 最低工資是多少
- 查詢平均工資最高的部門的 manager 的詳細資訊: last_name, department_id, email, salary
- 查詢 1999 年來公司的人所有員工的最高工資的那個員工的資訊.
- 返回其它部門中比job_id為‘IT_PROG’部門所有工資都低的員工的員工號、姓名、job_id 以及salary
************************answers*********************
- 查詢每個月倒數第 2 天入職的員工的資訊.
select last_name, hire_date
from employees
where hire_date = last_day(hire_date) – 1
- 查詢出 last_name 為 ‘Chen’ 的 manager 的資訊.
1). 通過兩條 sql 查詢:
select manager_id
from employees
where lower(last_name) = ‘chen’ –返回的結果為 108
select *
from employees
where employee_id = 108
2). 通過一條 sql 查詢(自連線):
select m.*
from employees e, employees m
where e.manager_id = m.employee_id and e.last_name = ‘Chen’
3). 通過一條 sql 查詢(子查詢):
select *
from employees
where employee_id = (
select manager_id
from employees
where last_name = ‘Chen’
)
- 查詢平均工資高於 8000 的部門 id 和它的平均工資.
SELECT department_id, avg(salary)
FROM employees e
GROUP BY department_id
HAVING avg(salary) > 8000
- 查詢工資最低的員工資訊: last_name, salary
SELECT last_name, salary
FROM employees
WHERE salary = (
SELECT min(salary)
FROM employees
)
- 查詢平均工資最低的部門資訊
SELECT *
FROM departments
WHERE department_id = (
SELECT department_id
FROM employees
GROUP BY department_id
HAVING avg(salary) = (
SELECT min(avg(salary))
FROM employees
GROUP BY department_id
)
)
- 查詢平均工資最低的部門資訊和該部門的平均工資
select d.*, (select avg(salary) from employees where department_id = d.department_id)
from departments d
where d.department_id = (
SELECT department_id
FROM employees
GROUP BY department_id
HAVING avg(salary) = (
SELECT min(avg(salary))
FROM employees
GROUP BY department_id
)
)
- 查詢平均工資最高的 job 資訊
1). 按 job_id 分組, 查詢最高的平均工資
SELECT max(avg(salary))
FROM employees
GROUP BY job_id
2). 查詢出平均工資等於 1) 的 job_id
SELECT job_id
FROM employees
GROUP BY job_id
HAVING avg(salary) = (
SELECT max(avg(salary))
FROM employees
GROUP BY job_id
)
3). 查詢出 2) 對應的 job 資訊
SELECT *
FROM jobs
WHERE job_id = (
SELECT job_id
FROM employees
GROUP BY job_id
HAVING avg(salary) = (
SELECT max(avg(salary))
FROM employees
GROUP BY job_id
)
)
- 查詢平均工資高於公司平均工資的部門有哪些?
1). 查詢出公司的平均工資
SELECT avg(salary)
FROM employees
2). 查詢平均工資高於 1) 的部門 ID
SELECT department_id
FROM employees
GROUP BY department_id
HAVING avg(salary) > (
SELECT avg(salary)
FROM employees
)
- 查詢出公司中所有 manager 的詳細資訊.
1). 查詢出所有的 manager_id
SELECT distinct manager_id
FROM employeess
2). 查詢出 employee_id 為 1) 查詢結果的那些員工的資訊
SELECT employee_id, last_name
FROM employees
WHERE employee_id in (
SELECT distinct manager_id
FROM employees
)
- 各個部門中 最高工資中最低的那個部門的 最低工資是多少
1). 查詢出各個部門的最高工資
SELECT max(salary)
FROM employees
GROUP BY department_id
2). 查詢出 1) 對應的查詢結果的最低值: 各個部門中最低的最高工資(無法查詢對應的 department_id)
SELECT min(max(salary))
FROM employees
GROUP BY department_id
3). 查詢出 2) 所對應的部門 id 是多少: 各個部門中最高工資等於 2) 的那個部門的 id
SELECT department_id
FROM employees
GROUP BY department_id
HAVING max(salary) = (
SELECT min(max(salary))
FROM employees
GROUP BY department_id
)
4). 查詢出 3) 所在部門的最低工資
SELECT min(salary)
FROM employees
WHERE department_id = (
SELECT department_id
FROM employees
GROUP BY department_id
HAVING max(salary) = (
SELECT min(max(salary))
FROM employees
GROUP BY department_id
)
)
- 查詢平均工資最高的部門的 manager 的詳細資訊: last_name, department_id, email, salary
1). 各個部門中, 查詢平均工資最高的平均工資是多少
SELECT max(avg(salary))
FROM employees
GROUP BY department_id
2). 各個部門中, 平均工資等於 1) 的那個部門的部門號是多少
SELECT department_id
FROM employees
GROUP BY department_id
HAVING avg(salary) = (
SELECT max(avg(salary))
FROM employees
GROUP BY department_id
)
3). 查詢出 2) 對應的部門的 manager_id
SELECT manager_id
FROM departments
WHERE department_id = (
SELECT department_id
FROM employees
GROUP BY department_id
HAVING avg(salary) = (
SELECT max(avg(salary))
FROM employees
GROUP BY department_id
)
)
4). 查詢出 employee_id 為 3) 查詢的 manager_id 的員工的 last_name, department_id, email, salary
SELECT last_name, department_id, email, salary
FROM employees
WHERE employee_id = (
SELECT manager_id
FROM departments
WHERE department_id = (
SELECT department_id
FROM employees
GROUP BY department_id
HAVING avg(salary) = (
SELECT max(avg(salary))
FROM employees
GROUP BY department_id
)
)
)
- 查詢 1999 年來公司的人所有員工的最高工資的那個員工的資訊.
1). 查詢出 1999 年來公司的所有的員工的 salary
SELECT salary
FROM employees
WHERE to_char(hire_date, ‘yyyy’) = ‘1999’
2). 查詢出 1) 對應的結果的最大值
SELECT max(salary)
FROM employees
WHERE to_char(hire_date, ‘yyyy’) = ‘1999’
3). 查詢工資等於 2) 對應的結果且 1999 年入職的員工資訊
SELECT *
FROM employees
WHERE to_char(hire_date, ‘yyyy’) = ‘1999’ AND salary = (
SELECT max(salary)
FROM employees
WHERE to_char(hire_date, ‘yyyy’) = ‘1999’
)
- 返回其它部門中比job_id為‘IT_PROG’部門所有工資都低的員工的員工號、姓名、job_id 以及salary
SELECT employee_id, last_name, job_id, salary
FROM employees
WHERE salary < ALL
(SELECT salary
FROM employees
WHERE job_id = ‘IT_PROG’)
AND job_id <> ‘IT_PROG’;
******************高階子查詢******************
- 書寫多列子查詢
- 在 FROM 子句中使用子查詢
- 在SQL中使用單列子查詢
- 書寫相關子查詢
- 使用 EXISTS 和 NOT EXISTS 操作符
- 使用子查詢更新和刪除資料
- 使用 WITH 子句
–多列子查詢（不成對比較 & 成對比較）
- 查詢與141號或174號員工的manager_id和department_id相同的其他員工的employee_id, manager_id, department_id
[方式一]
SELECT employee_id, manager_id, department_id
FROM employees
WHERE manager_id IN
(SELECT manager_id
FROM employees
WHERE employee_id IN (174,141))
AND department_id IN
(SELECT department_id
FROM employees
WHERE employee_id IN (174,141))
AND employee_id NOT IN(174,141);
[方式二]
SELECT employee_id, manager_id, department_id
FROM employees
WHERE (manager_id, department_id) IN
(SELECT manager_id, department_id
FROM employees
WHERE employee_id IN (141,174))
AND employee_id NOT IN (141,174);
–在 FROM 子句中使用子查詢
- 返回比本部門平均工資高的員工的last_name, department_id, salary及平均工資
[方式一]
select last_name,department_id,salary,
(select avg(salary)from employees e3
where e1.department_id = e3.department_id
group by department_id) avg_salary
from employees e1
where salary >
(select avg(salary)
from employees e2
where e1.department_id = e2.department_id
–group by department_id
)
[方式二]
SELECT a.last_name, a.salary,
a.department_id, b.salavg
FROM employees a, (SELECT department_id,
AVG(salary) salavg
FROM employees
GROUP BY department_id) b
WHERE a.department_id = b.department_id
AND a.salary > b.salavg;
—單列子查詢表示式
- Oracle8i只在下列情況下可以使用, 例如:SELECT 語句 (FROM 和WHERE 子句)INSERT 語句中的VALUES列表中
- Oracle9i中單列子查詢表示式可在下列情況下使用:DECODE 和 CASESELECT 中除 GROUP BY 子句以外的所有子句中
- 顯式員工的employee_id,last_name和location。其中，若員工department_id與location_id為1800的department_id相同，則location為’Canada’,其餘則為’USA’。
SELECT employee_id, last_name,
(CASE department_id
WHEN (SELECT department_id FROM departments
WHERE location_id = 1800)
THEN ‘Canada’ ELSE ‘USA’ END) location
FROM employees;
- 查詢員工的employee_id,last_name,要求按照員工的department_name排序
SELECT employee_id, last_name
FROM employees e
ORDER BY (SELECT department_name
FROM departments d
WHERE e.department_id = d.department_id);
—相關子查詢
5.查詢員工中工資大於本部門平均工資的員工的last_name,
salary和其department_id
SELECT last_name, salary, department_id
FROM employees outer
WHERE salary >
(SELECT AVG(salary)
FROM employees
WHERE department_id =
outer.department_id) ;
- 若employees表中employee_id與job_history表中employee_id相同的數目不小於2，輸出這些相同id的員工的employee_id,last_name和其job_id
SELECT e.employee_id, last_name,e.job_id
FROM employees e
WHERE 2 <= (SELECT COUNT(*)
FROM job_history
WHERE employee_id = e.employee_id);
—EXISTS 操作符
- EXISTS 操作符檢查在子查詢中是否存在滿足條件的行
- 如果在子查詢中存在滿足條件的行:不在子查詢中繼續查詢條件返回 TRUE
- 查詢公司管理者的employee_id,last_name,job_id,
department_id資訊
SELECT employee_id, last_name, job_id, department_id
FROM employees outer
WHERE EXISTS ( SELECT ‘X’
FROM employees
WHERE manager_id =
outer.employee_id);
- 查詢departments表中，不存在於employees表中的部門的department_id和department_name
SELECT department_id, department_name
FROM departments d
WHERE NOT EXISTS (SELECT ‘X’
FROM employees
WHERE department_id
= d.department_id);
–關於資料更新
9.修改表employees,新增department_name列，賦予department_id相應的部門名稱。
ALTER TABLE employees
ADD(department_name VARCHAR2(14));
UPDATE employees e
SET department_name =
(SELECT department_name
FROM departments d
WHERE e.department_id = d.department_id);
–關於資料刪除
10.刪除表employees中，其與emp_history表皆有的資料
DELETE FROM employees E
WHERE employee_id in
(SELECT employee_id
FROM emp_history
WHERE employee_id = E.employee_id);
—WITH 子句
- 查詢公司中各部門的總工資大於公司中各部門的平均總工資的部門資訊
WITH
dept_costs AS (
SELECT d.department_name, SUM(e.salary) AS dept_total
FROM employees e, departments d
WHERE e.department_id = d.department_id
GROUP BY d.department_name),
avg_cost AS (
SELECT SUM(dept_total)/COUNT(*) AS dept_avg
FROM dept_costs)
SELECT *
FROM dept_costs
WHERE dept_total >
(SELECT dept_avg
FROM avg_cost)
ORDER BY department_name;
附加題目：
12.查詢員工的last_name, department_id, salary.其中員工的salary,department_id與有獎金的任何一個員工的salary,
department_id相同即可
selectlast_name,department_id,salary
fromemployees
where(salary,department_id)in(
selectsalary,department_id
fromemployees
wherecommission_pctisnotnull
)
13.選擇工資大於所有JOB_ID = ‘SA_MAN’的員工的工資的員工的last_name, job_id, salary
selectlast_name,job_id,salary
fromemployees
wheresalary>all(
select salary
from employees
where job_id = ‘SA_MAN’
)
14.選擇所有沒有管理者的員工的last_name
selectlast_name
fromemployeese1
wherenotexists(
select ‘A’
from employees e2
where e1.manager_id = e2.employee_id
)
- 查詢10，50，20號部門的job_id，department_id並且department_id按10，50，20的順序排列
Column dummy noprint;
select job_id , department_id ,1 dummy
from employees
where department_id = 10
union
select job_id , department_id , 2
from employees
where department_id = 50
union
select job_id , department_id , 3
from employees
where department_id= 20
order by 3
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