Manage Employment Data

practice update, alter, replace, insert keywords.

Link

将id=5以及emp_no=10001的行数据替换成id=5_牛客题霸_牛客网www.nowcoder.com

Create Table and insert Data

CREATE TABLE titles_test (
   id int(11) not null primary key,
   emp_no  int(11) NOT NULL,
   title  varchar(50) NOT NULL,
   from_date  date NOT NULL,
   to_date  date DEFAULT NULL);

insert into titles_test values
('1', '10001', 'Senior Engineer', '1986-06-26', '9999-01-01'),
('2', '10002', 'Staff', '1996-08-03', '9999-01-01'),
('3', '10003', 'Senior Engineer', '1995-12-03', '9999-01-01'),
('4', '10004', 'Senior Engineer', '1995-12-03', '9999-01-01'),
('5', '10001', 'Senior Engineer', '1986-06-26', '9999-01-01'),
('6', '10002', 'Staff', '1996-08-03', '9999-01-01'),
('7', '10003', 'Senior Engineer', '1995-12-03', '9999-01-01');


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`));

Questions

1. 将id=5以及emp_no=10001的行数据替换成id=5以及emp_no=10005,其他数据保持不变，使用replace实现，直接使用update会报错。（Using Update）

   update titles_test set emp_no = REPLACE(emp_no, 10001, 10005) where id=5

2. 将titles_test表名修改为titles_2017

   1. alter table table-name operation-name to ....

      alter table titles_test rename to titles_2017;

3. 将所有获取奖金的员工当前的薪水增加10%

   update salaries
   set salary = 1.1 * salary
   where to_date = '9999-01-01' and emp_no in (select emp_no
   from bouns
   );
   

4. 获取Employees中的first_name，查询按照first_name最后两个字母，按照升序进行排列

   select first_name 
   from employees
   order by right(first_name,2);

5. 按照dept_no进行汇总，属于同一个部门的emp_no按照逗号进行连接，结果给出dept_no以及连接出的结果, 预期结果:

   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`));
   如：
   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,'2001-08-02','9999-01-01');
   INSERT INTO salaries VALUES(10003,43699,'2000-12-01','2001-12-01');
   INSERT INTO salaries VALUES(10003,43311,'2001-12-01','9999-01-01');
   INSERT INTO salaries VALUES(10004,70698,'2000-11-27','2001-11-27');
   INSERT INTO salaries VALUES(10004,74057,'2001-11-27','9999-01-01');
   
   
   
   select avg(s1.salary) as avg_salary
   from salaries s1
   where s1.to_date ='9999-01-01' 
   and s1.salary not in (select max(s.salary)
       from salaries s
       where s.to_date ='9999-01-01'
   )
   and s1.salary not in (
   select min(s.salary)
       from salaries s
       where s.to_date ='9999-01-01'
   )
   ;
   ;

7. 按照dept_no进行汇总，属于同一个部门的emp_no按照逗号进行连接，结果给出dept_no以及连接出的结果, 预期结果:

   dept_no	employees
   d001	10001,10002
   d002	10006
   d003	10005
   d004	10003,10004
   d005	10007,10008,10010
   d006	10009,10010

   select d.dept_no, group_concat(d.emp_no )  as employees
   from dept_emp d
   group by d.dept_no;

Conclusion

1. 更新table row的数据： update

   update table_name set  column_name = ... where col_name = ...;

2. 更新table属性: alter

   # add column
   alter table  table_name add col_name, col_type;
   # drop column
   ALTER TABLE table_name DROP COLUMN column_name;
   # change column type
   ALTER TABLE table_name ALTER COLUMN column_name TYPE datatype;

3. SQL里面的group-concat() 函数相对于Spark里面的collect-list() 函数，把groupby分组后的列表里面的column的list聚集到一行里面

   select d.dept_no, group_concat(d.emp_no )  as employees
   from dept_emp d
   group by d.dept_no;