描述

现有员工表employees如下：

有员工奖金表emp_bonus:

有薪水表salaries:

• 其中bonus类型btype为1其奖金为薪水salary的10%，btype为2其奖金为薪水的20%，其他类型均为薪水的30%。 to_date='9999-01-01'表示当前薪水。
• 请你给出emp_no、first_name、last_name、奖金类型btype、对应的当前薪水情况salary以及奖金金额bonus。
• bonus结果保留一位小数，输出结果按emp_no升序排序。

以上数据集的输出结果如下:

示例1:

drop table if exists  `employees` ; 
drop table if exists  emp_bonus; 
drop table if exists  `salaries` ; 
CREATE TABLE `employees` (
  `emp_no` int(11) NOT NULL,
  `birth_date` date NOT NULL,
  `first_name` varchar(14) NOT NULL,
  `last_name` varchar(16) NOT NULL,
  `gender` char(1) NOT NULL,
  `hire_date` date NOT NULL,
  PRIMARY KEY (`emp_no`));
 create table emp_bonus(
emp_no int not null,
recevied datetime not null,
btype smallint not null);
CREATE TABLE `salaries` (
`emp_no` int(11) NOT NULL,
`salary` int(11) NOT NULL,
`from_date` date NOT NULL,
`to_date` date NOT NULL,
PRIMARY KEY (`emp_no`,`from_date`));
insert into emp_bonus values
(10001, '2010-01-01',1),
(10002, '2010-10-01',2);
INSERT INTO employees VALUES(10001,'1953-09-02','Georgi','Facello','M','1986-06-26');
INSERT INTO employees VALUES(10002,'1964-06-02','Bezalel','Simmel','F','1985-11-21');

INSERT INTO salaries VALUES(10001,60117,'1986-06-26','1987-06-26');
INSERT INTO salaries VALUES(10001,62102,'1987-06-26','1988-06-25');
INSERT INTO salaries VALUES(10001,66074,'1988-06-25','1989-06-25');
INSERT INTO salaries VALUES(10001,66596,'1989-06-25','1990-06-25');
INSERT INTO salaries VALUES(10001,66961,'1990-06-25','1991-06-25');
INSERT INTO salaries VALUES(10001,71046,'1991-06-25','1992-06-24');
INSERT INTO salaries VALUES(10001,74333,'1992-06-24','1993-06-24');
INSERT INTO salaries VALUES(10001,75286,'1993-06-24','1994-06-24');
INSERT INTO salaries VALUES(10001,75994,'1994-06-24','1995-06-24');
INSERT INTO salaries VALUES(10001,76884,'1995-06-24','1996-06-23');
INSERT INTO salaries VALUES(10001,80013,'1996-06-23','1997-06-23');
INSERT INTO salaries VALUES(10001,81025,'1997-06-23','1998-06-23');
INSERT INTO salaries VALUES(10001,81097,'1998-06-23','1999-06-23');
INSERT INTO salaries VALUES(10001,84917,'1999-06-23','2000-06-22');
INSERT INTO salaries VALUES(10001,85112,'2000-06-22','2001-06-22');
INSERT INTO salaries VALUES(10001,85097,'2001-06-22','2002-06-22');
INSERT INTO salaries VALUES(10001,88958,'2002-06-22','9999-01-01');
INSERT INTO salaries VALUES(10002,72527,'1996-08-03','1997-08-03');
INSERT INTO salaries VALUES(10002,72527,'1997-08-03','1998-08-03');
INSERT INTO salaries VALUES(10002,72527,'1998-08-03','1999-08-03');
INSERT INTO salaries VALUES(10002,72527,'1999-08-03','2000-08-02');
INSERT INTO salaries VALUES(10002,72527,'2000-08-02','2001-08-02');
INSERT INTO salaries VALUES(10002,72527,'2001-08-02','9999-01-01');

输出：

10001|Georgi|Facello|1|88958|8895.8
10002|Bezalel|Simmel|2|72527|14505.4

我的解题思路：

这题比较简单，主要考察表连接，相同字段可以使用using连接

1.找出员工的当前薪水

select emp_no,
       salary
from salaries
where to_date = '9999-01-01'

2.表内连接，之后使用case when 求出奖金

case e2.btype
   when 1 then round(salary * 0.1, 1)
   when 2 then round(salary * 0.2, 1)
   else round(salary * 0.3, 1) end as bonus

完整代码：

select e1.emp_no,
       first_name,
       last_name,
       e2.btype,
       e3.salary,
       case e2.btype
           when 1 then round(salary * 0.1, 1)
           when 2 then round(salary * 0.2, 1)
           else round(salary * 0.3, 1) end as bonus
from employees e1
         inner join emp_bonus e2 using (emp_no)
         inner join (select emp_no,
                           salary
                    from salaries
                    where to_date = '9999-01-01') e3
                   using (emp_no)
;