Mysql 数据库（五）
1 插入数据：
create table 新表名（字段 数据类型[约束条间]。。。） select 字段。。。 from 旧表名
create table 新表名（字段 数据类型[约束条件]。。。） select 字段 as 别名 from 旧表名 [where 条件]；
as 起一个别名，起别名时，默认有as 所以可以不用加as 就可以起别名。
mysql> create table t1(id int primary key auto_increment,
-> name char(10) not null,
-> age int not null);
Query OK, 0 rows affected (0.38 sec)
mysql> insert into t1(name,age)values('fang',18),('haiyan',17),('dong',21);
Query OK, 3 rows affected (0.06 sec)
Records: 3 Duplicates: 0 Warnings: 0
mysql> desc t1;
+-------+----------+------+-----+---------+----------------+
| Field | Type | Null | Key | Default | Extra |
+-------+----------+------+-----+---------+----------------+
| id | int(11) | NO | PRI | NULL | auto_increment |
| name | char(10) | NO | | NULL | |
| age | int(11) | NO | | NULL | |
+-------+----------+------+-----+---------+----------------+
3 rows in set (0.00 sec)
mysql> select * from t1;
+----+--------+-----+
| id | name | age |
+----+--------+-----+
| 1 | fang | 18 |
| 2 | haiyan | 17 |
| 3 | dong | 21 |
+----+--------+-----+
3 rows in set (0.00 sec)
mysql> create table t2(name char(10) not null,
-> age int not null) select name,age from t1;
Query OK, 3 rows affected (0.32 sec)
Records: 3 Duplicates: 0 Warnings: 0
mysql> desc t2;
+-------+----------+------+-----+---------+-------+
| Field | Type | Null | Key | Default | Extra |
+-------+----------+------+-----+---------+-------+
| name | char(10) | NO | | NULL | |
| age | int(11) | NO | | NULL | |
+-------+----------+------+-----+---------+-------+
2 rows in set (0.00 sec)
mysql> select * from t2;
+--------+-----+
| name | age |
+--------+-----+
| fang | 18 |
| haiyan | 17 |
| dong | 21 |
+--------+-----+
3 rows in set (0.00 sec)
mysql> create table t3(x char(10) not null,
-> a int not null) select name as x,age a from t1;
Query OK, 3 rows affected (0.31 sec)
Records: 3 Duplicates: 0 Warnings: 0
mysql> desc t3;
+-------+----------+------+-----+---------+-------+
| Field | Type | Null | Key | Default | Extra |
+-------+----------+------+-----+---------+-------+
| x | char(10) | NO | | NULL | |
| a | int(11) | NO | | NULL | |
+-------+----------+------+-----+---------+-------+
2 rows in set (0.00 sec)
mysql> select * from t3;
+--------+----+
| x | a |
+--------+----+
| fang | 18 |
| haiyan | 17 |
| dong | 21 |
+--------+----+
3 rows in set (0.00 sec)
2 修改数据：
update 表名 set 字段=记录 where 条件；
mysql> create table t1(id int primary key auto_increment,
-> name char(10) not null,
-> age int not null);
Query OK, 0 rows affected (0.38 sec)
mysql> insert into t1(name,age)values('fang',18),('haiyan',17),('dong',21);
Query OK, 3 rows affected (0.06 sec)
Records: 3 Duplicates: 0 Warnings: 0
mysql> desc t1;
+-------+----------+------+-----+---------+----------------+
| Field | Type | Null | Key | Default | Extra |
+-------+----------+------+-----+---------+----------------+
| id | int(11) | NO | PRI | NULL | auto_increment |
| name | char(10) | NO | | NULL | |
| age | int(11) | NO | | NULL | |
+-------+----------+------+-----+---------+----------------+
3 rows in set (0.00 sec)
mysql> select * from t1;
+----+--------+-----+
| id | name | age |
+----+--------+-----+
| 1 | fang | 18 |
| 2 | haiyan | 17 |
| 3 | dong | 21 |
+----+--------+-----+
3 rows in set (0.00 sec)
mysql> update t1 set name='jie' where id=3 and age=21;
Query OK, 1 row affected (0.08 sec)
Rows matched: 1 Changed: 1 Warnings: 0
mysql> select * from t1;
+----+--------+-----+
| id | name | age |
+----+--------+-----+
| 1 | fang | 18 |
| 2 | haiyan | 17 |
| 3 | jie | 21 |
+----+--------+-----+
3 rows in set (0.00 sec)
3
concat：字符串的拼接，可以拼成任意的格式
concat_ws：第一个参数指定的是分割符，后面加上自己要看的字段
\G：将乱了的记录重新按行显示。
二 常用的select查看
select 的基本格式：
select distinot：去重 字段名。。。 from 表名
where 约束条件 ：取出来的记录默认为是一个组，在这里就可以使用聚合函数，约束条件就是默认某些字段的约束。
group by 字段名 ：后面加上某个字段，就会按照那个字段分组，分组过后可以直接查看分组的字段，要想查看其他的字段，必须要借助聚合函数，分组是为了一类一类的处理数据。而分组的字段是依据字段的约束条件不唯一。
having 过滤语句 ：只能跟在分组的后面，处理一些分组过后的约束条件。
order by 字段 排序 ：排序。后面加上需要按照排序的字段，后面可以同时加上多个排序条件，如果前面的排序有重复的，才会执行后面的，如果没有重复的，后面的就不会执行。他是在取出了相应字段的记录后才开始执行的。
limit 限制条件 ：规定查看的范围，在最后才开始运行。
准备表：
mysql> use day44;
Database changed
mysql> create table employee(
-> 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 (0.28 sec)
mysql>
mysql>
mysql> #查看表结构
mysql> desc employee;
+--------------+-----------------------+------+-----+---------+----------------+
| Field | Type | Null | Key | Default | Extra |
+--------------+-----------------------+------+-----+---------+----------------+
| id | int(11) | NO | PRI | NULL | auto_increment |
| name | varchar(20) | NO | | NULL | |
| sex | enum('male','female') | NO | | male | |
| age | int(3) unsigned | NO | | 28 | |
| hire_date | date | NO | | NULL | |
| post | varchar(50) | YES | | NULL | |
| post_comment | varchar(100) | YES | | NULL | |
| salary | double(15,2) | YES | | NULL | |
| office | int(11) | YES | | NULL | |
| depart_id | int(11) | YES | | NULL | |
+--------------+-----------------------+------+-----+---------+----------------+
10 rows in set (0.01 sec)
mysql>
mysql> #插入记录
mysql> #三个部门：教学，销售，运营
mysql> insert into employee(name,sex,age,hire_date,post,salary,office,depart_id) values
-> ('egon','male',18,'20170301','老男孩驻沙河办事处外交大使',7300.33,401,1), #以下是教学部
-> ('alex','male',78,'20150302','teacher',1000000.31,401,1),
-> ('wupeiqi','male',81,'20130305','teacher',8300,401,1),
-> ('yuanhao','male',73,'20140701','teacher',3500,401,1),
-> ('liwenzhou','male',28,'20121101','teacher',2100,401,1),
-> ('jingliyang','female',18,'20110211','teacher',9000,401,1),
-> ('jinxin','male',18,'19000301','teacher',30000,401,1),
-> ('成龙','male',48,'20101111','teacher',10000,401,1),
->
-> ('歪歪','female',48,'20150311','sale',3000.13,402,2),#以下是销售部门
-> ('丫丫','female',38,'20101101','sale',2000.35,402,2),
-> ('丁丁','female',18,'20110312','sale',1000.37,402,2),
-> ('星星','female',18,'20160513','sale',3000.29,402,2),
-> ('格格','female',28,'20170127','sale',4000.33,402,2),
->
-> ('张野','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 (0.09 sec)
Records: 18 Duplicates: 0 Warnings: 0
集合函数：min：最小值 max：最大值 avg：计算平均值 sum：计算总和 count：计算个数
where 条件约束：后面可以加上比较符号（> < = != <> <= >=） 逻辑运算符（and or not）
in：什么或什么或什么 between：在什么和什么之间 like：像什么 后面出入两个符号 % ：任意多个字符 _ ：表示任意一个字符 is：什么是什么
mysql> select * from employee where age>50; +----+---------+------+-----+------------+---------+--------------+------------+--------+-----------+ | id | name | sex | age | hire_date | post | post_comment | salary | office | depart_id | +----+---------+------+-----+------------+---------+--------------+------------+--------+-----------+ | 2 | alex | male | 78 | 2015-03-02 | teacher | NULL | 1000000.31 | 401 | 1 | | 3 | wupeiqi | male | 81 | 2013-03-05 | teacher | NULL | 8300.00 | 401 | 1 | | 4 | yuanhao | male | 73 | 2014-07-01 | teacher | NULL | 3500.00 | 401 | 1 | +----+---------+------+-----+------------+---------+--------------+------------+--------+-----------+ 3 rows in set (0.00 sec) mysql> select * from employee where sex='male' and salary>30000; +----+------+------+-----+------------+---------+--------------+------------+--------+-----------+ | id | name | sex | age | hire_date | post | post_comment | salary | office | depart_id | +----+------+------+-----+------------+---------+--------------+------------+--------+-----------+ | 2 | alex | male | 78 | 2015-03-02 | teacher | NULL | 1000000.31 | 401 | 1 | +----+------+------+-----+------------+---------+--------------+------------+--------+-----------+ 1 row in set (0.00 sec) mysql> select * from employee where post='teacher' or salary>30000; +----+------------+--------+-----+------------+---------+--------------+------------+--------+-----------+ | id | name | sex | age | hire_date | post | post_comment | salary | office | depart_id | +----+------------+--------+-----+------------+---------+--------------+------------+--------+-----------+ | 2 | alex | male | 78 | 2015-03-02 | teacher | NULL | 1000000.31 | 401 | 1 | | 3 | wupeiqi | male | 81 | 2013-03-05 | teacher | NULL | 8300.00 | 401 | 1 | | 4 | yuanhao | male | 73 | 2014-07-01 | teacher | NULL | 3500.00 | 401 | 1 | | 5 | liwenzhou | male | 28 | 2012-11-01 | teacher | NULL | 2100.00 | 401 | 1 | | 6 | jingliyang | female | 18 | 2011-02-11 | teacher | NULL | 9000.00 | 401 | 1 | | 7 | jinxin | male | 18 | 1900-03-01 | teacher | NULL | 30000.00 | 401 | 1 | | 8 | 成龙 | male | 48 | 2010-11-11 | teacher | NULL | 10000.00 | 401 | 1 | +----+------------+--------+-----+------------+---------+--------------+------------+--------+-----------+ 7 rows in set (0.00 sec) mysql> select * from employee where age between 20 and 30; +----+-----------+--------+-----+------------+-----------+--------------+----------+--------+-----------+ | id | name | sex | age | hire_date | post | post_comment | salary | office | depart_id | +----+-----------+--------+-----+------------+-----------+--------------+----------+--------+-----------+ | 5 | liwenzhou | male | 28 | 2012-11-01 | teacher | NULL | 2100.00 | 401 | 1 | | 13 | 格格 | female | 28 | 2017-01-27 | sale | NULL | 4000.33 | 402 | 2 | | 14 | 张野 | male | 28 | 2016-03-11 | operation | NULL | 10000.13 | 403 | 3 | +----+-----------+--------+-----+------------+-----------+--------------+----------+--------+-----------+ 3 rows in set (0.01 sec) mysql> select * from employee where id in(3,6,16) or name like '程%'; +----+------------+--------+-----+------------+-----------+--------------+----------+--------+-----------+ | id | name | sex | age | hire_date | post | post_comment | salary | office | depart_id | +----+------------+--------+-----+------------+-----------+--------------+----------+--------+-----------+ | 3 | wupeiqi | male | 81 | 2013-03-05 | teacher | NULL | 8300.00 | 401 | 1 | | 6 | jingliyang | female | 18 | 2011-02-11 | teacher | NULL | 9000.00 | 401 | 1 | | 15 | 程咬金 | male | 18 | 1997-03-12 | operation | NULL | 20000.00 | 403 | 3 | | 16 | 程咬银 | female | 18 | 2013-03-11 | operation | NULL | 19000.00 | 403 | 3 | | 17 | 程咬铜 | male | 18 | 2015-04-11 | operation | NULL | 18000.00 | 403 | 3 | | 18 | 程咬铁 | female | 18 | 2014-05-12 | operation | NULL | 17000.00 | 403 | 3 | +----+------------+--------+-----+------------+-----------+--------------+----------+--------+-----------+ 6 rows in set (0.44 sec)
group by 分组：后面加上一个字段名
mysql> select post,count(id),group_concat(name) from employee group by post; +----------------------------+-----------+-------------------------------------------------------+ | post | count(id) | group_concat(name) | +----------------------------+-----------+-------------------------------------------------------+ | operation | 5 | 张野,程咬金,程咬银,程咬铜,程咬铁 | | sale | 5 | 歪歪,丫丫,丁丁,星星,格格 | | teacher | 7 | alex,wupeiqi,yuanhao,liwenzhou,jingliyang,jinxin,成龙 | | 老男孩驻沙河办事处外交大使 | 1 | egon | +----------------------------+-----------+-------------------------------------------------------+ 4 rows in set (0.00 sec) mysql> select post,min(salary) from employee group by post; +----------------------------+-------------+ | post | min(salary) | +----------------------------+-------------+ | operation | 10000.13 | | sale | 1000.37 | | teacher | 2100.00 | | 老男孩驻沙河办事处外交大使 | 7300.33 | +----------------------------+-------------+ 4 rows in set (0.00 sec) mysql> select post,max(salary) from employee group by post; +----------------------------+-------------+ | post | max(salary) | +----------------------------+-------------+ | operation | 20000.00 | | sale | 4000.33 | | teacher | 1000000.31 | | 老男孩驻沙河办事处外交大使 | 7300.33 | +----------------------------+-------------+ 4 rows in set (0.00 sec) mysql> select post,sum(salary) from employee group by post; +----------------------------+-------------+ | post | sum(salary) | +----------------------------+-------------+ | operation | 84000.13 | | sale | 13001.47 | | teacher | 1062900.31 | | 老男孩驻沙河办事处外交大使 | 7300.33 | +----------------------------+-------------+ 4 rows in set (0.00 sec) mysql> select post,avg(salary) from employee group by post; +----------------------------+---------------+ | post | avg(salary) | +----------------------------+---------------+ | operation | 16800.026000 | | sale | 2600.294000 | | teacher | 151842.901429 | | 老男孩驻沙河办事处外交大使 | 7300.330000 | +----------------------------+---------------+ 4 rows in set (0.00 sec)
having 过滤条件：后面加的内容和where一样的，不过需要借助于聚合函数过滤记录
mysql> select post from employee group by post having count(id)>5; +---------+ | post | +---------+ | teacher | +---------+ 1 row in set (0.00 sec) mysql> select post from employee group by post having count(id)>5 or avg(salary) >10000; +-----------+ | post | +-----------+ | operation | | teacher | +-----------+ 2 rows in set (0.00 sec)
order by ：后面跟上：asc：升序，从小到大排序 ； desc：降序，从大到小排序。order by：默认是从小到达排序的。
mysql> select * from employee order by age asc,id desc; +----+------------+--------+-----+------------+----------------------------+--------------+------------+--------+-----------+ | id | name | sex | age | hire_date | post | post_comment | salary | office | depart_id | +----+------------+--------+-----+------------+----------------------------+--------------+------------+--------+-----------+ | 18 | 程咬铁 | female | 18 | 2014-05-12 | operation | NULL | 17000.00 | 403 | 3 | | 17 | 程咬铜 | male | 18 | 2015-04-11 | operation | NULL | 18000.00 | 403 | 3 | | 16 | 程咬银 | female | 18 | 2013-03-11 | operation | NULL | 19000.00 | 403 | 3 | | 15 | 程咬金 | male | 18 | 1997-03-12 | operation | NULL | 20000.00 | 403 | 3 | | 12 | 星星 | female | 18 | 2016-05-13 | sale | NULL | 3000.29 | 402 | 2 | | 11 | 丁丁 | female | 18 | 2011-03-12 | sale | NULL | 1000.37 | 402 | 2 | | 7 | jinxin | male | 18 | 1900-03-01 | teacher | NULL | 30000.00 | 401 | 1 | | 6 | jingliyang | female | 18 | 2011-02-11 | teacher | NULL | 9000.00 | 401 | 1 | | 1 | egon | male | 18 | 2017-03-01 | 老男孩驻沙河办事处外交大使 | NULL | 7300.33 | 401 | 1 | | 14 | 张野 | male | 28 | 2016-03-11 | operation | NULL | 10000.13 | 403 | 3 | | 13 | 格格 | female | 28 | 2017-01-27 | sale | NULL | 4000.33 | 402 | 2 | | 5 | liwenzhou | male | 28 | 2012-11-01 | teacher | NULL | 2100.00 | 401 | 1 | | 10 | 丫丫 | female | 38 | 2010-11-01 | sale | NULL | 2000.35 | 402 | 2 | | 9 | 歪歪 | female | 48 | 2015-03-11 | sale | NULL | 3000.13 | 402 | 2 | | 8 | 成龙 | male | 48 | 2010-11-11 | teacher | NULL | 10000.00 | 401 | 1 | | 4 | yuanhao | male | 73 | 2014-07-01 | teacher | NULL | 3500.00 | 401 | 1 | | 2 | alex | male | 78 | 2015-03-02 | teacher | NULL | 1000000.31 | 401 | 1 | | 3 | wupeiqi | male | 81 | 2013-03-05 | teacher | NULL | 8300.00 | 401 | 1 | +----+------------+--------+-----+------------+----------------------------+--------------+------------+--------+-----------+ 18 rows in set (0.00 sec)
limit 限制条件：后面输入整数类型，只传一个值是查看记录的条数，默认从第1条记录开始查看，如果出入两个数，第一个数是初始值，就是从那一条的下一条开始查看，第二个数就是查看记录的条数。
mysql> select * from employee where id limit 6,10; +----+--------+--------+-----+------------+-----------+--------------+----------+--------+-----------+ | id | name | sex | age | hire_date | post | post_comment | salary | office | depart_id | +----+--------+--------+-----+------------+-----------+--------------+----------+--------+-----------+ | 7 | jinxin | male | 18 | 1900-03-01 | teacher | NULL | 30000.00 | 401 | 1 | | 8 | 成龙 | male | 48 | 2010-11-11 | teacher | NULL | 10000.00 | 401 | 1 | | 9 | 歪歪 | female | 48 | 2015-03-11 | sale | NULL | 3000.13 | 402 | 2 | | 10 | 丫丫 | female | 38 | 2010-11-01 | sale | NULL | 2000.35 | 402 | 2 | | 11 | 丁丁 | female | 18 | 2011-03-12 | sale | NULL | 1000.37 | 402 | 2 | | 12 | 星星 | female | 18 | 2016-05-13 | sale | NULL | 3000.29 | 402 | 2 | | 13 | 格格 | female | 28 | 2017-01-27 | sale | NULL | 4000.33 | 402 | 2 | | 14 | 张野 | male | 28 | 2016-03-11 | operation | NULL | 10000.13 | 403 | 3 | | 15 | 程咬金 | male | 18 | 1997-03-12 | operation | NULL | 20000.00 | 403 | 3 | | 16 | 程咬银 | female | 18 | 2013-03-11 | operation | NULL | 19000.00 | 403 | 3 | +----+--------+--------+-----+------------+-----------+--------------+----------+--------+-----------+ 10 rows in set (0.00 sec)
他们的执行顺序是：from——》where—》group by—》having—》distinct—》order—》limit。如果上一个没有顺序还是不会改变
distinct：去掉重复
only_full_group_by：使用方法 set @@lobal sql_mode='only_full_group_by' 修改全局的一条信息
where后面还可以跟上regexp：正则表达式条件约束，regexp后面跟的内容和正则表达式里面的内容差不多
mysql> select * from employee where name regexp 'a.'; +----+------------+--------+-----+------------+---------+--------------+------------+--------+-----------+ | id | name | sex | age | hire_date | post | post_comment | salary | office | depart_id | +----+------------+--------+-----+------------+---------+--------------+------------+--------+-----------+ | 2 | alex | male | 78 | 2015-03-02 | teacher | NULL | 1000000.31 | 401 | 1 | | 4 | yuanhao | male | 73 | 2014-07-01 | teacher | NULL | 3500.00 | 401 | 1 | | 6 | jingliyang | female | 18 | 2011-02-11 | teacher | NULL | 9000.00 | 401 | 1 | +----+------------+--------+-----+------------+---------+--------------+------------+--------+-----------+ 3 rows in set (0.05 sec) mysql> select * from employee where name regexp '^a.'; +----+------+------+-----+------------+---------+--------------+------------+--------+-----------+ | id | name | sex | age | hire_date | post | post_comment | salary | office | depart_id | +----+------+------+-----+------------+---------+--------------+------------+--------+-----------+ | 2 | alex | male | 78 | 2015-03-02 | teacher | NULL | 1000000.31 | 401 | 1 | +----+------+------+-----+------------+---------+--------------+------------+--------+-----------+ 1 row in set (0.00 sec) mysql> select * from employee where name regexp '^j.'; +----+------------+--------+-----+------------+---------+--------------+----------+--------+-----------+ | id | name | sex | age | hire_date | post | post_comment | salary | office | depart_id | +----+------------+--------+-----+------------+---------+--------------+----------+--------+-----------+ | 6 | jingliyang | female | 18 | 2011-02-11 | teacher | NULL | 9000.00 | 401 | 1 | | 7 | jinxin | male | 18 | 1900-03-01 | teacher | NULL | 30000.00 | 401 | 1 | +----+------------+--------+-----+------------+---------+--------------+----------+--------+-----------+ 2 rows in set (0.00 sec) mysql> select * from employee where name regexp '^j.*n$'; +----+--------+------+-----+------------+---------+--------------+----------+--------+-----------+ | id | name | sex | age | hire_date | post | post_comment | salary | office | depart_id | +----+--------+------+-----+------------+---------+--------------+----------+--------+-----------+ | 7 | jinxin | male | 18 | 1900-03-01 | teacher | NULL | 30000.00 | 401 | 1 | +----+--------+------+-----+------------+---------+--------------+----------+--------+-----------+ 1 row in set (0.00 sec) mysql> select * from employee where name REGEXP '^jin.*[n|g]$'; +----+------------+--------+-----+------------+---------+--------------+----------+--------+-----------+ | id | name | sex | age | hire_date | post | post_comment | salary | office | depart_id | +----+------------+--------+-----+------------+---------+--------------+----------+--------+-----------+ | 6 | jingliyang | female | 18 | 2011-02-11 | teacher | NULL | 9000.00 | 401 | 1 | | 7 | jinxin | male | 18 | 1900-03-01 | teacher | NULL | 30000.00 | 401 | 1 | +----+------------+--------+-----+------------+---------+--------------+----------+--------+-----------+ 2 rows in set (0.00 sec)
练习题：
USE day44;
-- 1 查出所有员工的名字，薪资,格式为
-- <名字:egon> <薪资:3000>
SELECT '姓名：',name,'薪资：',salary from employee;
-- 2 查出所有的岗位（去掉重复）
select distinct(post) from employee;
-- 3 查出所有员工名字，以及他们的年薪,年薪的字段名为annual_year
SELECT name,salary*12 as annual_year from employee;
-- 1. 查看岗位是teacher的员工姓名、年龄
select name,age from employee where post='teacher';
-- 2. 查看岗位是teacher且年龄大于30岁的员工姓名、年龄
select name,age from employee where post='teacher' and age>30;
-- 3. 查看岗位是teacher且薪资在9000-1000范围内的员工姓名、年龄、薪资
select name,age,salary from employee
where post='teacher' and salary BETWEEN 9000 and 10000;
-- 4. 查看岗位描述不为NULL的员工信息
select * from employee where not null;
-- 5. 查看岗位是teacher且薪资是10000或9000或30000的员工姓名、年龄、薪资
select * from employee where post='teacher' and salary in (10000,9000,30000);
-- 6. 查看岗位是teacher且薪资不是10000或9000或30000的员工姓名、年龄、薪资
select * from employee where post='teacher' and salary not in(10000,9000,30000);
-- 7. 查看岗位是teacher且名字是jin开头的员工姓名、年薪
select * from employee where name like 'jin%';
-- 1. 查询岗位名以及岗位包含的所有员工名字
select post,group_concat(name) from employee group by post;
-- 2. 查询岗位名以及各岗位内包含的员工个数
select post,count(id) from employee group by post;
-- 3. 查询公司内男员工和女员工的个数
select sex,count(id) from employee group by sex;
-- 4. 查询岗位名以及各岗位的平均薪资
select post,avg(salary) from employee group by post;
-- 5. 查询岗位名以及各岗位的最高薪资
select post,max(salary) from employee GROUP BY post;
-- 6. 查询岗位名以及各岗位的最低薪资
select post,min(salary) from employee GROUP BY post;
-- 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
select sex,avg(salary) from employee group by sex;
-- 1. 查询各岗位内包含的员工个数小于2的岗位名、岗位内包含员工名字、个数
select post,group_concat(name),count(id) from employee group by post having count(id)<2;
-- 3. 查询各岗位平均薪资大于10000的岗位名、平均工资
select post,avg(salary) from employee group by post having avg(salary)>10000;
-- 4. 查询各岗位平均薪资大于10000且小于20000的岗位名、平均工资
SELECT post,avg(salary) from employee group by post
having avg(salary)>10000 and avg(salary)<20000;
-- 1. 查询所有员工信息，先按照age升序排序，如果age相同则按照hire_date降序排序
select * from employee order by age asc,hire_date desc;
-- 2. 查询各岗位平均薪资大于10000的岗位名、平均工资,结果按平均薪资升序排列
select post,avg(salary)as a from employee group by post
having avg(salary)>10000 order by a asc;
-- 3. 查询各岗位平均薪资大于10000的岗位名、平均工资,结果按平均薪资降序排列
select post,avg(salary) a from employee group by post
having avg(salary) >10000 order by a desc;
-- 查看所有员工中名字是jin开头，n或者g结果的员工信息
select * from employee where name REGEXP '^jin.*[n|g]$';
