＃第九章 子查询课后习题

#第九章 子查询课后习题

#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=(
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 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 JOIN departments
ON employees.department_id=departments.department_id
WHERE location_id=1700;

#6.查询管理者是King的员工姓名和工资
SELECT e1.last_name,e1.salary
FROM employees e1 JOIN
employees e2
ON e1.manager_id=e2.employee_id
AND e1.manager_id IN(
SELECT employee_id
FROM employees
WHERE last_name=‘King’
);

#下面更好的方法
SELECT last_name,salary
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
SELECT department_id,AVG(salary)
FROM employees
GROUP BY department_id
HAVING AVG(salary)<=ALL(
SELECT AVG(salary)
FROM employees
GROUP BY department_id
);

#下面是简便方法求部门最低平均工资但无法显示部门
SELECT MIN(avg_sal)
FROM (
SELECT AVG(salary) avg_sal
FROM employees
GROUP BY department_id
)t_dept_avgsal

#success
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
)
);

#方式二：
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：用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）
SELECT department_id,AVG(salary)
FROM employees e1
GROUP BY department_id
HAVING AVG(salary)<=ALL(
SELECT AVG(salary)
FROM employees
GROUP BY department_id
);

#10.查询平均工资最高的 job 信息
SELECT job_id,AVG(salary)
FROM employees
GROUP BY job_id
HAVING AVG(salary)>=ALL(
SELECT AVG(salary)
FROM employees
GROUP BY 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,AVG(salary)
FROM employees
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
SELECT e1.last_name,e1.employee_id
FROM employees e1
WHERE e1.employee_id IN(
SELECT manager_id
FROM employees
);

SELECT DISTINCT e1.last_name,e1.employee_id
FROM employees e1, employees e2
WHERE e1.employee_id=e2.manager_id;

#13.各个部门中最高工资中最低的工资 ，所在部门的最低工资是多少?
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
)
);

#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
SELECT employee_id,last_name,department_id,email,salary
FROM employees
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)
);

#只查询一条结果
SELECT employee_id,last_name,department_id,email,salary
FROM employees
GROUP BY department_id
HAVING AVG(salary)>=ALL(
SELECT AVG(salary)
FROM employees
GROUP BY department_id
);

#工资最高的部门信息
SELECT AVG(salary),department_id
FROM employees
GROUP BY department_id
HAVING AVG(salary)>=ALL(
SELECT AVG(salary)
FROM employees
GROUP BY department_id);

#工资最低的部门信息
SELECT AVG(salary),department_id
FROM employees
GROUP BY department_id
HAVING AVG(salary)<=ALL(
SELECT AVG(salary)
FROM employees
GROUP BY 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
SELECT department_id
FROM departments
WHERE department_id NOT IN(
SELECT DISTINCT department_id
FROM employees
WHERE job_id=‘ST_CLEPK’
);

#16. 选择所有没有管理者的员工的last_name
SELECT last_name
FROM employees
WHERE manager_id<=>NULL;

#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’
SELECT employee_id,last_name,hire_date,salary
FROM employees
WHERE manager_id=(
SELECT employee_id
FROM employees
WHERE last_name=‘De Haan’
);

#方式二
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）
#让他们两个department_id相等来限制在相同的部门之中
SELECT employee_id,last_name,salary
FROM employees e1
WHERE salary>(
SELECT AVG(salary)
FROM employees e2
WHERE e1.department_id=e2.department_id
);

#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 (SELECT COUNT(*)
FROM employees e
WHERE d.department_id=e.department_id)>5;

#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 country_id
FROM countries
WHERE region_id IN(
SELECT region_id
FROM countries
WHERE region_id>2
)

SELECT * FROM locations;

#下面是所给答案
SELECT country_id
FROM locations l
WHERE 2<(SELECT COUNT(*)
FROM departments d
WHERE l.location_id=d.location_id);