MySQL子查询课后练习

4.4 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=(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 e1
WHERE EXISTS (SELECT * FROM employees e2 
WHERE e1.department_id=e2.department_id
AND e1.employee_id<>e2.employee_id
AND e2.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 e JOIN departments d
ON e.department_id = d.department_id
WHERE location_id=1700;
#6.查询管理者是King的员工姓名和工资
SELECT last_name,salary
FROM employees
WHERE manager_id =ANY(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<=ALL(SELECT salary FROM employees);
#8.查询平均工资最低的部门信息
#方法一
SELECT d.*
FROM departments d
WHERE d.department_id=(SELECT department_id
			FROM employees e
			GROUP BY department_id
			HAVING AVG(salary)<=ALL(SELECT AVG(salary)
						FROM employees
                                                GROUP BY department_id
			                        )
                        ）
#方法二
SELECT d.*
FROM departments d
WHERE d.department_id = (
			  SELECT department_id
    			  FROM employees e
    			  GROUP BY department_id
    			  HAVING AVG(salary)=(SELECT MIN(avg_sal)
                                              FROM employees e2,(SELECT department_id,AVG(salary) avg_sal																		        
                                              FROM employees e2
				              GROUP BY department_id)	t_avg_sal
                           WHERE e2.department_id=t_avg_sal.department_id
						)
	
			)
#方法三使用limit
SELECT d.*
FROM departments d
WHERE d.department_id = (
    		        SELECT department_id
    			FROM employees e
    			GROUP BY department_id
    			HAVING AVG(salary)=(SELECT AVG(salary) avg_sal
                                           FROM employees
                                           GROUP BY department_id
                                           ORDER BY avg_sal
                                           LIMIT 1)
    			)
#方法四
SELECT d.*
FROM departments d,(SELECT department_id,AVG(salary) avg_sal	
                    FROM employees											    
		    GROUP BY department_id
		    ORDER BY avg_sal
                    LIMIT 1) t_avg_sal
WHERE d.department_id = t_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 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
                    LIMIT 1) t_avg_sal
WHERE d.department_id = t_avg_sal.department_id;
#10.查询平均工资最高的 job 信息
SELECT j.*
FROM jobs j,(SELECT job_id,AVG(salary) avg_sal
	    FROM employees
	    GROUP BY job_id
	    ORDER BY avg_sal
	    LIMIT 1) t_avg_sal
WHERE j.job_id=t_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,AVG(salary) 
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
SELECT DISTINCT e2.*
FROM employees e1,employees e2
WHERE e1.manager_id = e2.employee_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?
SELECT d.*,(SELECT MAX(salary) FROM employees WHERE department_id=d.department_id) max_sal
FROM departments d,(SELECT department_id,MAX(salary) max_sal
                    FROM employees
                    GROUP BY department_id
                    ORDER BY max_sal
                    LIMIT 1) t_max_sal
WHERE d.department_id=t_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
SELECT DISTINCT e2.last_name, e2.department_id, e2.email, e2.salary
FROM employees e1,employees e2,(SELECT department_id,AVG(salary)avg_sal
				FROM employees
				GROUP BY department_id
				ORDER BY avg_sal DESC
				LIMIT 1) t_avg_sal
WHERE e1.manager_id = e2.employee_id
AND e1.department_id = t_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
SELECT DISTINCT d.department_id
FROM employees e,departments d
WHERE e.department_id=d.department_id
AND e.job_id<>'ST_CLERK'

#方式二
SELECT DISTINCT d.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
WHERE manager_id IS 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 e
WHERE e.manager_id =(SELECT employee_id
		     FROM employees
		     WHERE 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）
SELECT employee_id,last_name, salary
FROM employees e
WHERE salary>(SELECT AVG(salary)
             FROM employees e2
             WHERE e.department_id = e2.department_id
             GROUP BY 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 d.department_name
FROM departments d
WHERE 5< (SELECT COUNT(*)
          FROM employees e
	  WHERE e.department_id=d.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 l.country_id
FROM locations l 
WHERE 2< (SELECT COUNT(*)
	  FROM departments d
	  WHERE d.location_id=l.location_id)