oracle習題練習

1. 查詢所員工的email全名,公司email 統一以 "@zpark.cn" 結尾
   select email || ‘@zpark.cn’ from employees;
2. 按照入職日期由新到舊排列員工信息
   select employee_id,first_name,last_name,email,phone_number,hire_date,job_id,salary,commission_pct,manager_id,department_id from employees order by hire_date;
3. 查詢80號部門工資大於7000的員工的全名與工資.
   select first_name || ’ ‘ || last_name as name, salary from employees where department_id = 80 and salary > 7000;
4. 查詢所有last_name 由四個以上字母組成的員工信息
   select * from employees where last_name like’____%’;

單行函數練習

1. 把hiredate列看做是員工的生日,查詢本月過生日的員工(考察知識點:單行函數)
   select * from employees where to_char(hire_date, ‘mm’) = to_char(sysdate, ‘mm’);
2. 請用三種以上的方式查詢2002年入職的員工(考察知識點:單行函數)
   ①select * from employees where to_char(hire_date, ‘yyyy’) = ‘2002’;
   ②select * from employees where hire_date between to_date(‘2002-1-1’, ‘yyyy-mm-dd’) and to_date(‘2002-12-30’, ‘yyyy-mm-dd’);
   ③select * from employees where hire_date >= to_date(‘2002-1-1’, ‘yyyy-mm-dd’) and hire_date <= to_date(‘2002-12-30’, ‘yyyy-mm-dd’);
3. 查詢2002年下半年入職的員工(考察知識點:單行函數)
   select * from employees where hire_date between to_date(‘2002-7-1’, ‘yyyy-mm-dd’) and to_date(‘2002-12-30’, ‘yyyy-mm-dd’);
4. 打印自己出生了多少天
   select to_date(to_char(sysdate, 'yyyy-mm-dd'), 'yyyy-mm-dd') - to_date('1996-3-1', 'yyyy-mm-dd') from dual;

組函數練習

1. 求1997年各個月入職的的員工個數(考察知識點:組函數)
   select count(*), to_char(hire_date, 'mm') from employees where to_char(hire_date, 'yyyy') = '2002' group by to_char(hire_date, 'mm');
2. 查詢50號部門,60號部門,70號部門的平均工資
   select avg(salary), department_id from employees where department_id in(50, 60, 70) group by department_id;
3. 查詢平均工資高於8000元的部門的最高工資.
   select max(salary), department_id from employees group by department_id having avg(salary) > 8000;
4. 統計公司里經理的人數
   ①select count(count(manager_id)), manager_id from employees where manager_id is not null group by manager_id;
   ②select count(distinct manager_id) from employees;

分頁查詢練習

查詢工資排名第5到第10的員工信息
select * from (select employee_id, first_name, rownum as rn from (select * from employees order by salary desc)) where rn >= 5 and rn <= 10;

子查詢練習

1. 查詢工資大於本部門平均工資的員工基本信息
   select * from (select * from employees group by department_id having salary > avg(salary));
2. 顯示與30號部門first_name為’Guy’員工工資相同的員工姓名和工資
   select first_name, salary from employees where salary = (select salary from employees where department_id = 30 and first_name = ‘Guy’);
3. 查詢各個職位員工工資大於平均工資(平均工資包括所有員工)的人數和員工職位
   select count(*), job_id from employees where salary > (select avg(salary) from employees) group by job_id;

表連接查詢練習

1. 顯示所有職員的姓名及其所在部門的名稱和工資
   select employees.first_name, department_name, salary from employees left outer join departments on employees.department_id = departments.department_id;
2. 查詢在研發部('IT')工作員工的編號，姓名，工作部門，工作所在地
   select employees.employee_id, employees.first_name ,employees.department_id from (employees left outer join departments on employees.department_id = departments.department_id ) left outer join locations on departments.location_id = locations.location_id
3. 查詢各個部門的名稱和員工人數
   select departments.department_name, count(*) from employees left join departments on employees.department_id = departments.department_id group by departments.department_name;
4. 查詢員工的基本信息，附加其上級的姓名
   select e1.employee_id, e1.first_name, e1.salary, e2.first_name from employees e1 left join employees e2 on e1.manager_id = e2.employee_id
5. 求入職日期相同（年月日相同）的員工(考察知識點:自連接)(有重復)
   select e1.first_name, e2.first_name from employees e1 inner join employees e2 on e1.hire_date = e2.hire_date and e1.first_name != e2.first_name
   where e1.employee_id < e2.employee_id; --(去重)
6. 顯示各個部門經理的基本工資
   select employees.employee_id, salary from departments left outer join employees on departments.manager_id = employees.employee_id