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第09章_子查询的课后练习
2026-09-26
MySQL
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第09章_子查询的课后练习

#1.查询和Zlotkey相同部门的员工姓名和工资

SELECT last_name,salary
FROM employees
WHERE department_id IN (
SELECT department_id
FROM employees
WHERE last_name = 'Zlotkey'
);

#2.查询工资比公司平均工资高的员工的员工号，姓名和工资。

SELECT employee_id,last_name,salary
FROM employees
WHERE salary > (
SELECT AVG(salary)
FROM employees
);

#3.选择工资大于所有JOB_ID = 'SA_MAN'的员工的工资的员工的last_name, job_id, salary

SELECT last_name,job_id,salary
FROM employees
WHERE salary > ALL(
SELECT salary
FROM employees
WHERE job_id = 'SA_MAN'
);

#4.查询和姓名中包含字母u的员工在相同部门的员工的员工号和姓名

SELECT employee_id,last_name
FROM employees
WHERE department_id IN (
SELECT DISTINCT department_id
FROM employees
WHERE last_name LIKE '%u%'
);

#5.查询在部门的location_id为1700的部门工作的员工的员工号

SELECT employee_id
FROM employees
WHERE department_id IN (
SELECT department_id
FROM departments
WHERE location_id = 1700
);

#6.查询管理者是King的员工姓名和工资

SELECT last_name,salary,manager_id
FROM employees
WHERE manager_id IN (
SELECT employee_id
FROM employees
WHERE last_name = 'King'
);

#7.查询工资最低的员工信息: last_name, salary

SELECT last_name,salary
FROM employees
WHERE salary = (
SELECT MIN(salary)
FROM employees
);

#8.查询平均工资最低的部门信息
#方式1：
SELECT *
FROM departments
WHERE department_id = (
SELECT department_id
FROM employees
GROUP BY department_id
HAVING AVG(salary ) = (
SELECT MIN(avg_sal)
FROM (
SELECT AVG(salary) avg_sal
FROM employees
GROUP BY department_id
) t_dept_avg_sal

					)
		);

#方式2：

SELECT *
FROM departments
WHERE department_id = (
SELECT department_id
FROM employees
GROUP BY department_id
HAVING AVG(salary ) <= ALL(
SELECT AVG(salary)
FROM employees
GROUP BY department_id
)
);

#方式3： LIMIT

SELECT *
FROM departments
WHERE department_id = (
SELECT department_id
FROM employees
GROUP BY department_id
HAVING AVG(salary ) =(
SELECT AVG(salary) avg_sal
FROM employees
GROUP BY department_id
ORDER BY avg_sal ASC
LIMIT 1
)
);

#方式4：

SELECT d.*
FROM departments d,(
SELECT department_id,AVG(salary) avg_sal
FROM employees
GROUP BY department_id
ORDER BY avg_sal ASC
LIMIT 0,1
) t_dept_avg_sal
WHERE d.department_id = t_dept_avg_sal.department_id

#9.查询平均工资最低的部门信息和该部门的平均工资（相关子查询）
#方式1：
SELECT d.*,(SELECT AVG(salary) FROM employees WHERE department_id = d.department_id) avg_sal
FROM departments d
WHERE department_id = (
SELECT department_id
FROM employees
GROUP BY department_id
HAVING AVG(salary ) = (
SELECT MIN(avg_sal)
FROM (
SELECT AVG(salary) avg_sal
FROM employees
GROUP BY department_id
) t_dept_avg_sal

					)
		);

#方式2：

SELECT d.*,(SELECT AVG(salary) FROM employees WHERE department_id = d.department_id) avg_sal
FROM departments d
WHERE department_id = (
SELECT department_id
FROM employees
GROUP BY department_id
HAVING AVG(salary ) <= ALL(
SELECT AVG(salary)
FROM employees
GROUP BY department_id
)
);

#方式3： LIMIT

SELECT d.*,(SELECT AVG(salary) FROM employees WHERE department_id = d.department_id) avg_sal
FROM departments d
WHERE department_id = (
SELECT department_id
FROM employees
GROUP BY department_id
HAVING AVG(salary ) =(
SELECT AVG(salary) avg_sal
FROM employees
GROUP BY department_id
ORDER BY avg_sal ASC
LIMIT 1
)
);

#方式4：

SELECT d.*,(SELECT AVG(salary) FROM employees WHERE department_id = d.department_id) avg_sal
FROM departments d,(
SELECT department_id,AVG(salary) avg_sal
FROM employees
GROUP BY department_id
ORDER BY avg_sal ASC
LIMIT 0,1
) t_dept_avg_sal
WHERE d.department_id = t_dept_avg_sal.department_id

#10.查询平均工资最高的 job 信息

#方式1：
SELECT *
FROM jobs
WHERE job_id = (
SELECT job_id
FROM employees
GROUP BY job_id
HAVING AVG(salary) = (
SELECT MAX(avg_sal)
FROM (
SELECT AVG(salary) avg_sal
FROM employees
GROUP BY job_id
) t_job_avg_sal
)
);

#方式2：
SELECT *
FROM jobs
WHERE job_id = (
SELECT job_id
FROM employees
GROUP BY job_id
HAVING AVG(salary) >= ALL(
SELECT AVG(salary)
FROM employees
GROUP BY job_id
)
);

#方式3：
SELECT *
FROM jobs
WHERE job_id = (
SELECT job_id
FROM employees
GROUP BY job_id
HAVING AVG(salary) =(
SELECT AVG(salary) avg_sal
FROM employees
GROUP BY job_id
ORDER BY avg_sal DESC
LIMIT 0,1
)
);

#方式4：
SELECT j.*
FROM jobs j,(
SELECT job_id,AVG(salary) avg_sal
FROM employees
GROUP BY job_id
ORDER BY avg_sal DESC
LIMIT 0,1
) t_job_avg_sal
WHERE j.job_id = t_job_avg_sal.job_id

#11.查询平均工资高于公司平均工资的部门有哪些?

SELECT department_id
FROM employees
WHERE department_id IS NOT NULL
GROUP BY department_id
HAVING AVG(salary) > (
SELECT AVG(salary)
FROM employees
);

#12.查询出公司中所有 manager 的详细信息

#方式1：自连接 xxx worked for yyy
SELECT DISTINCT mgr.employee_id,mgr.last_name,mgr.job_id,mgr.department_id
FROM employees emp JOIN employees mgr
ON emp.manager_id = mgr.employee_id;

#方式2：子查询

SELECT employee_id,last_name,job_id,department_id
FROM employees
WHERE employee_id IN (
SELECT DISTINCT manager_id
FROM employees
);

#方式3：使用EXISTS
SELECT employee_id,last_name,job_id,department_id
FROM employees e1
WHERE EXISTS (
SELECT *
FROM employees e2
WHERE e1.employee_id = e2.manager_id
);

#13.各个部门中 最高工资中最低的那个部门的 最低工资是多少?

#方式1：
SELECT MIN(salary)
FROM employees
WHERE department_id = (
SELECT department_id
FROM employees
GROUP BY department_id
HAVING MAX(salary) = (
SELECT MIN(max_sal)
FROM (
SELECT MAX(salary) max_sal
FROM employees
GROUP BY department_id
) t_dept_max_sal
)
);

SELECT *
FROM employees
WHERE department_id = 10;

#方式2：
SELECT MIN(salary)
FROM employees
WHERE department_id = (
SELECT department_id
FROM employees
GROUP BY department_id
HAVING MAX(salary) <= ALL (
SELECT MAX(salary)
FROM employees
GROUP BY department_id
)
);

#方式3：
SELECT MIN(salary)
FROM employees
WHERE department_id = (
SELECT department_id
FROM employees
GROUP BY department_id
HAVING MAX(salary) = (
SELECT MAX(salary) max_sal
FROM employees
GROUP BY department_id
ORDER BY max_sal ASC
LIMIT 0,1
)
);

#方式4：
SELECT MIN(salary)
FROM employees e,(
SELECT department_id,MAX(salary) max_sal
FROM employees
GROUP BY department_id
ORDER BY max_sal ASC
LIMIT 0,1
) t_dept_max_sal
WHERE e.department_id = t_dept_max_sal.department_id

#14.查询平均工资最高的部门的 manager 的详细信息: last_name, department_id, email, salary
#方式1：
SELECT last_name, department_id, email, salary
FROM employees
WHERE employee_id = ANY (
SELECT DISTINCT manager_id
FROM employees
WHERE department_id = (
SELECT department_id
FROM employees
GROUP BY department_id
HAVING AVG(salary) = (
SELECT MAX(avg_sal)
FROM (
SELECT AVG(salary) avg_sal
FROM employees
GROUP BY department_id
) t_dept_avg_sal
)
)
);

#方式2：
SELECT last_name, department_id, email, salary
FROM employees
WHERE employee_id = ANY (
SELECT DISTINCT manager_id
FROM employees
WHERE department_id = (
SELECT department_id
FROM employees
GROUP BY department_id
HAVING AVG(salary) >= ALL (
SELECT AVG(salary) avg_sal
FROM employees
GROUP BY department_id
)
)
);

#方式3：
SELECT last_name, department_id, email, salary
FROM employees
WHERE employee_id IN (
SELECT DISTINCT manager_id
FROM employees e,(
SELECT department_id,AVG(salary) avg_sal
FROM employees
GROUP BY department_id
ORDER BY avg_sal DESC
LIMIT 0,1
) t_dept_avg_sal
WHERE e.department_id = t_dept_avg_sal.department_id
);

#15. 查询部门的部门号，其中不包括job_id是"ST_CLERK"的部门号
#方式1：
SELECT department_id
FROM departments
WHERE department_id NOT IN (
SELECT DISTINCT department_id
FROM employees
WHERE job_id = 'ST_CLERK'
);

#方式2：
SELECT department_id
FROM departments d
WHERE NOT EXISTS (
SELECT *
FROM employees e
WHERE d.department_id = e.department_id
AND e.job_id = 'ST_CLERK'
);

#16. 选择所有没有管理者的员工的last_name

SELECT last_name
FROM employees emp
WHERE NOT EXISTS (
SELECT *
FROM employees mgr
WHERE emp.manager_id = mgr.employee_id
);

#17．查询员工号、姓名、雇用时间、工资，其中员工的管理者为 'De Haan'
#方式1：
SELECT employee_id,last_name,hire_date,salary
FROM employees
WHERE manager_id IN (
SELECT employee_id
FROM employees
WHERE last_name = 'De Haan'
);

#方式2：
SELECT employee_id,last_name,hire_date,salary
FROM employees e1
WHERE EXISTS (
SELECT *
FROM employees e2
WHERE e1.manager_id = e2.employee_id
AND e2.last_name = 'De Haan'
);

#18.查询各部门中工资比本部门平均工资高的员工的员工号, 姓名和工资（相关子查询）

#方式1：使用相关子查询
SELECT last_name,salary,department_id
FROM employees e1
WHERE salary > (
SELECT AVG(salary)
FROM employees e2
WHERE department_id = e1.department_id
);

#方式2：在FROM中声明子查询
SELECT e.last_name,e.salary,e.department_id
FROM employees e,(
SELECT department_id,AVG(salary) avg_sal
FROM employees
GROUP BY department_id) t_dept_avg_sal
WHERE e.department_id = t_dept_avg_sal.department_id
AND e.salary > t_dept_avg_sal.avg_sal

#19.查询每个部门下的部门人数大于 5 的部门名称（相关子查询）

SELECT department_name
FROM departments d
WHERE 5 < (
SELECT COUNT(*)
FROM employees e
WHERE d.department_id = e.department_id
);

#20.查询每个国家下的部门个数大于 2 的国家编号（相关子查询）

SELECT * FROM locations;

SELECT country_id
FROM locations l
WHERE 2 < (
SELECT COUNT(*)
FROM departments d
WHERE l.location_id = d.location_id
);

/*
子查询的编写技巧（或步骤）：① 从里往外写 ② 从外往里写

如何选择？
① 如果子查询相对较简单，建议从外往里写。一旦子查询结构较复杂，则建议从里往外写
② 如果是相关子查询的话，通常都是从外往里写。

*/

第09章_子查询的课后练习
https://www.clxhxhhr.top/posts/4534/
作者
clxstart
发布于
2026-09-26
许可协议
CC BY-NC-SA 4.0
第09章_子查询
SHOW CREATE DATABASE mytest2;
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