每日作业5/6

1.整理今日内容
2.完成下列分组查询练习题(以课上建表代码为参考)

mysql> create table emp(
    ->   id int not null unique auto_increment,
    ->   name varchar(20) not null,
    ->   sex enum('male','female') not null default 'male', #大部分是男的
    ->   age int(3) unsigned not null default 28,
    ->   hire_date date not null,
    ->   post varchar(50),
    ->   post_comment varchar(100),
    ->   salary double(15,2),
    ->   office int, #一个部门一个屋子
    ->   depart_id int
    -> );
Query OK, 0 rows affected (0.00 sec)

mysql> insert into emp(name,sex,age,hire_date,post,salary,office,depart_id) values
    -> ('jason','male',18,'20170301','张江第一帅形象代言',7300.33,401,1), #以下是教学部
    -> ('tom','male',78,'20150302','teacher',1000000.31,401,1),
    -> ('kevin','male',81,'20130305','teacher',8300,401,1),
    -> ('tony','male',73,'20140701','teacher',3500,401,1),
    -> ('owen','male',28,'20121101','teacher',2100,401,1),
    -> ('jack','female',18,'20110211','teacher',9000,401,1),
    -> ('jenny','male',18,'19000301','teacher',30000,401,1),
    -> ('sank','male',48,'20101111','teacher',10000,401,1),
    -> ('哈哈','female',48,'20150311','sale',3000.13,402,2),#以下是销售部门
    -> ('呵呵','female',38,'20101101','sale',2000.35,402,2),
    -> ('西西','female',18,'20110312','sale',1000.37,402,2),
    -> ('乐乐','female',18,'20160513','sale',3000.29,402,2),
    -> ('拉拉','female',28,'20170127','sale',4000.33,402,2),
    -> ('僧龙','male',28,'20160311','operation',10000.13,403,3), #以下是运营部门
    -> ('程咬金','male',18,'19970312','operation',20000,403,3),
    -> ('程咬银','female',18,'20130311','operation',19000,403,3),
    -> ('程咬铜','male',18,'20150411','operation',18000,403,3),
    -> ('程咬铁','female',18,'20140512','operation',17000,403,3);
Query OK, 18 rows affected (0.00 sec)
Records: 18  Duplicates: 0  Warnings: 0

mysql>

1. 查询岗位名以及岗位包含的所有员工名字

mysql> select post as "部门名称",group_concat(name) as "员工" from emp group by post;
+-----------------------------+------------------------------------------------+
| 部门名称                    | 员工                                           |
+-----------------------------+------------------------------------------------+
| operation                   | 程咬铁,程咬铜,程咬银,程咬金,僧龙               |
| sale                        | 拉拉,乐乐,西西,呵呵,哈哈                       |
| teacher                     | sank,jenny,jack,owen,tony,kevin,tom            |
| 张江第一帅形象代言          | jason                                          |
+-----------------------------+------------------------------------------------+
4 rows in set (0.00 sec)

mysql> 

2. 查询岗位名以及各岗位内包含的员工个数

mysql> select post as "部门名称",count(id) as "员工人数" from emp group by post;
+-----------------------------+--------------+
| 部门名称                    | 员工人数     |
+-----------------------------+--------------+
| operation                   |            5 |
| sale                        |            5 |
| teacher                     |            7 |
| 张江第一帅形象代言          |            1 |
+-----------------------------+--------------+
4 rows in set (0.00 sec)

mysql> 

3. 查询公司内男员工和女员工的个数

mysql> select sex as "性别",count(id) as "人数" from emp group by sex;
+--------+--------+
| 性别   | 人数   |
+--------+--------+
| male 

4. 查询岗位名以及各岗位的平均薪资

mysql> select post as "岗位",avg(salary) as "平均薪资" from emp group by post;
+-----------------------------+---------------+
| 岗位                        | 平均薪资      |
+-----------------------------+---------------+
| operation                   |  16800.026000 |
| sale                        |   2600.294000 |
| teacher                     | 151842.901429 |
| 张江第一帅形象代言          |   7300.330000 |
+-----------------------------+---------------+
4 rows in set (0.00 sec)

mysql>

5. 查询岗位名以及各岗位的最高薪资

mysql> select post as "岗位",max(salary) as "最高薪资" from emp group by post;
+-----------------------------+--------------+
| 岗位                        | 最高薪资     |
+-----------------------------+--------------+
| operation                   |     20000.00 |
| sale                        |      4000.33 |
| teacher                     |   1000000.31 |
| 张江第一帅形象代言          |      7300.33 |
+-----------------------------+--------------+
4 rows in set (0.00 sec)

mysql> 

6. 查询岗位名以及各岗位的最低薪资

mysql> select post as "岗位",min(salary) as "最高薪资" from emp group by post;
+-----------------------------+--------------+
| 岗位                        | 最高薪资     |
+-----------------------------+--------------+
| operation                   |     10000.13 |
| sale                        |      1000.37 |
| teacher                     |      2100.00 |
| 张江第一帅形象代言          |      7300.33 |
+-----------------------------+--------------+
4 rows in set (0.00 sec)

mysql> 

7. 查询男员工与男员工的平均薪资，女员工与女员工的平均薪资

mysql> select sex as "性别",avg(salary) as "平均薪资" from emp group by sex;
+--------+---------------+
| 性别   | 平均薪资      |
+--------+---------------+
| male   | 110920.077000 |
| female |   7250.183750 |
+--------+---------------+
2 rows in set (0.00 sec)

mysql>

3.练习拼表操作并理解其意义
4.理解子查询思路体会其意义