day47-约束条件续，多表查询

前期表准备

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
);

#插入记录
#三个部门：教学，销售，运营
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);


# 当表字段特别多 展示的时候错乱 可以使用G分行展示
select * from empG;

# 个别同学的电脑在插入中文的时候还是会出现乱码或者空白的现象 你可以将字符编码统一设置成GBK

几个重要关键字的执行顺序

# 书写顺序
select id,name from emp where id > 3;
# 执行顺序
from
where
select

"""
虽然执行顺序和书写顺序不一致 你在写sql语句的时候可能不知道怎么写
你就按照书写顺序的方式写sql
    select * 先用*号占位
    之后去补全后面的sql语句
    最后将*号替换后你想要的具体字段
    
    明天会一直使用 这里先理解
"""

where筛选条件

# 作用:是对整体数据的一个筛选操作
# 1.查询id大于等于3小于等于6的数据
select id,name,age from emp where id>=3 and id<=6;
select id,name from emp where id between 3 and 6;  两者等价

mysql> select id,name,age from emp where id>=3 and id<=6;
+----+-------+-----+
| id | name | age |
+----+-------+-----+
| 3 | kevin | 81 |
| 4 | tony | 73 |
| 5 | owen | 28 |
| 6 | jack | 18 |
+----+-------+-----+
4 rows in set (0.00 sec)

mysql> select id,name,age from emp where id between 3 and 6;
+----+-------+-----+
| id | name | age |
+----+-------+-----+
| 3 | kevin | 81 |
| 4 | tony | 73 |
| 5 | owen | 28 |
| 6 | jack | 18 |
+----+-------+-----+
4 rows in set (0.00 sec)

mysql>

# 2.查询薪资是20000或者18000或者17000的数据
select * from emp where salary=20000 or salary=18000 or salary=17000;
select * from emp where salary in (20000,18000,17000);

mysql> select * from emp where salary=20000 or salary=17000 or salary= 18000;
+----+-----------+--------+-----+------------+-----------+--------------+----------+--------+-----------+
| id | name | sex | age | hire_date | post | post_comment | salary | office | depart_id |
+----+-----------+--------+-----+------------+-----------+--------------+----------+--------+-----------+
| 15 | 程咬金 | male | 18 | 1997-03-12 | operation | NULL | 20000.00 | 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 |
+----+-----------+--------+-----+------------+-----------+--------------+----------+--------+-----------+
3 rows in set (0.00 sec)

mysql> select * from emp where salary in (17000,18000,20000);
+----+-----------+--------+-----+------------+-----------+--------------+----------+--------+-----------+
| id | name | sex | age | hire_date | post | post_comment | salary | office | depart_id |
+----+-----------+--------+-----+------------+-----------+--------------+----------+--------+-----------+
| 15 | 程咬金 | male | 18 | 1997-03-12 | operation | NULL | 20000.00 | 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 |
+----+-----------+--------+-----+------------+-----------+--------------+----------+--------+-----------+
3 rows in set (0.00 sec)

mysql>

# 3.查询员工姓名中包含字母o的员工的姓名和薪资
"""
模糊查询
    like
        %  匹配任意多个字符
        _  匹配任意单个字符
"""
select name,salary from emp where name like '%o%';

mysql> select * from emp where name like '%o%';
+----+-------+------+-----+------------+-----------------------------+--------------+------------+--------+-----------+
| id | name | sex | age | hire_date | post | post_comment | salary | office | depart_id |
+----+-------+------+-----+------------+-----------------------------+--------------+------------+--------+-----------+
| 1 | jason | male | 18 | 2017-03-01 | 张江第一帅形象代言 | NULL | 7300.33 | 401 | 1 |
| 2 | tom | male | 78 | 2015-03-02 | teacher | NULL | 1000000.31 | 401 | 1 |
| 4 | tony | male | 73 | 2014-07-01 | teacher | NULL | 3500.00 | 401 | 1 |
| 5 | owen | male | 28 | 2012-11-01 | teacher | NULL | 2100.00 | 401 | 1 |
+----+-------+------+-----+------------+-----------------------------+--------------+------------+--------+-----------+
4 rows in set (0.00 sec)

mysql>

# 4.查询员工姓名是由四个字符组成的 姓名和薪资  char_length()   _
select name,salary from emp where name like '____';
select name,salary from emp where char_length(name) = 4;

mysql> select name,salary from emp where name like '____';
+------+----------+
| name | salary |
+------+----------+
| tony | 3500.00 |
| owen | 2100.00 |
| jack | 9000.00 |
| sank | 10000.00 |
+------+----------+
4 rows in set (0.00 sec)

mysql> select * from emp where char_length(name)=4;
+----+------+--------+-----+------------+---------+--------------+----------+--------+-----------+
| id | name | sex | age | hire_date | post | post_comment | salary | office | depart_id |
+----+------+--------+-----+------------+---------+--------------+----------+--------+-----------+
| 4 | tony | male | 73 | 2014-07-01 | teacher | NULL | 3500.00 | 401 | 1 |
| 5 | owen | male | 28 | 2012-11-01 | teacher | NULL | 2100.00 | 401 | 1 |
| 6 | jack | female | 18 | 2011-02-11 | teacher | NULL | 9000.00 | 401 | 1 |
| 8 | sank | male | 48 | 2010-11-11 | teacher | NULL | 10000.00 | 401 | 1 |
+----+------+--------+-----+------------+---------+--------------+----------+--------+-----------+
4 rows in set (0.00 sec)

mysql>

# 5.查询id小于3或者id大于6的数据
select * from emp where id not between 3 and 6;

mysql> select * from emp where id not between 4 and 6;
+----+-----------+--------+-----+------------+-----------------------------+--------------+------------+--------+-----------+
| id | name | sex | age | hire_date | post | post_comment | salary | office | depart_id |
+----+-----------+--------+-----+------------+-----------------------------+--------------+------------+--------+-----------+
| 1 | jason | male | 18 | 2017-03-01 | 张江第一帅形象代言 | NULL | 7300.33 | 401 | 1 |
| 2 | tom | male | 78 | 2015-03-02 | teacher | NULL | 1000000.31 | 401 | 1 |
| 3 | kevin | male | 81 | 2013-03-05 | teacher | NULL | 8300.00 | 401 | 1 |
| 7 | jenny | male | 18 | 1900-03-01 | teacher | NULL | 30000.00 | 401 | 1 |
| 8 | sank | male | 48 | 2010-11-11 | teacher | NULL | 10000.00 | 401 | 1 |
| 9 | 哈哈 | female | 48 | 2015-03-11 | sale | NULL | 3000.13 | 402 | 2 |
| 10 | 呵呵 | female | 38 | 2010-11-01 | sale | NULL | 2000.35 | 402 | 2 |
| 11 | 西西 | female | 18 | 2011-03-12 | sale | NULL | 1000.37 | 402 | 2 |
| 12 | 乐乐 | female | 18 | 2016-05-13 | sale | NULL | 3000.29 | 402 | 2 |
| 13 | 拉拉 | female | 28 | 2017-01-27 | sale | NULL | 4000.33 | 402 | 2 |
| 14 | 僧龙 | 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 |
| 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 |
+----+-----------+--------+-----+------------+-----------------------------+--------------+------------+--------+-----------+
15 rows in set (0.00 sec)

mysql>

# 6.查询薪资不在20000,18000,17000范围的数据
select * from emp where salary not in (20000,18000,17000);

mysql> select * from emp where salary not in (17000,18000,20000);
+----+-----------+--------+-----+------------+-----------------------------+--------------+------------+--------+-----------+
| id | name | sex | age | hire_date | post | post_comment | salary | office | depart_id |
+----+-----------+--------+-----+------------+-----------------------------+--------------+------------+--------+-----------+
| 1 | jason | male | 18 | 2017-03-01 | 张江第一帅形象代言 | NULL | 7300.33 | 401 | 1 |
| 2 | tom | male | 78 | 2015-03-02 | teacher | NULL | 1000000.31 | 401 | 1 |
| 3 | kevin | male | 81 | 2013-03-05 | teacher | NULL | 8300.00 | 401 | 1 |
| 4 | tony | male | 73 | 2014-07-01 | teacher | NULL | 3500.00 | 401 | 1 |
| 5 | owen | male | 28 | 2012-11-01 | teacher | NULL | 2100.00 | 401 | 1 |
| 6 | jack | female | 18 | 2011-02-11 | teacher | NULL | 9000.00 | 401 | 1 |
| 7 | jenny | male | 18 | 1900-03-01 | teacher | NULL | 30000.00 | 401 | 1 |
| 8 | sank | male | 48 | 2010-11-11 | teacher | NULL | 10000.00 | 401 | 1 |
| 9 | 哈哈 | female | 48 | 2015-03-11 | sale | NULL | 3000.13 | 402 | 2 |
| 10 | 呵呵 | female | 38 | 2010-11-01 | sale | NULL | 2000.35 | 402 | 2 |
| 11 | 西西 | female | 18 | 2011-03-12 | sale | NULL | 1000.37 | 402 | 2 |
| 12 | 乐乐 | female | 18 | 2016-05-13 | sale | NULL | 3000.29 | 402 | 2 |
| 13 | 拉拉 | female | 28 | 2017-01-27 | sale | NULL | 4000.33 | 402 | 2 |
| 14 | 僧龙 | male | 28 | 2016-03-11 | operation | NULL | 10000.13 | 403 | 3 |
| 16 | 程咬银 | female | 18 | 2013-03-11 | operation | NULL | 19000.00 | 403 | 3 |
+----+-----------+--------+-----+------------+-----------------------------+--------------+------------+--------+-----------+
15 rows in set (0.00 sec)

mysql>

# 7.查询岗位描述为空的员工姓名和岗位名  针对null不用等号 用is
select name,post from emp where post_comment = NULL;
select name,post from emp where post_comment is NULL;

mysql> select name,post from emp where post_comment =NULL;
Empty set (0.00 sec)

mysql> select name,post from emp where post_comment is NULL;
+-----------+-----------------------------+
| name | post |
+-----------+-----------------------------+
| jason | 张江第一帅形象代言 |
| tom | teacher |
| kevin | teacher |
| tony | teacher |
| owen | teacher |
| jack | teacher |
| jenny | teacher |
| sank | teacher |
| 哈哈 | sale |
| 呵呵 | sale |
| 西西 | sale |
| 乐乐 | sale |
| 拉拉 | sale |
| 僧龙 | operation |
| 程咬金 | operation |
| 程咬银 | operation |
| 程咬铜 | operation |
| 程咬铁 | operation |
+-----------+-----------------------------+
18 rows in set (0.00 sec)

mysql>

group by分组

# 分组实际应用场景  分组应用场景非常的多
    男女比例
    部门平均薪资
    部门秃头率
    国家之间数据统计

# 1    按照部门分组
select * from emp group by post;
mysql> select * from emp group by post;
+----+--------+--------+-----+------------+-----------------------------+--------------+------------+--------+-----------+
| id | name   | sex    | age | hire_date  | post                        | post_comment | salary     | office | depart_id |
+----+--------+--------+-----+------------+-----------------------------+--------------+------------+--------+-----------+
| 14 | 僧龙   | male   |  28 | 2016-03-11 | operation                   | NULL         |   10000.13 |    403 |         3 |
|  9 | 哈哈   | female |  48 | 2015-03-11 | sale                        | NULL         |    3000.13 |    402 |         2 |
|  2 | tom    | male   |  78 | 2015-03-02 | teacher                     | NULL         | 1000000.31 |    401 |         1 |
|  1 | jason  | male   |  18 | 2017-03-01 | 张江第一帅形象代言          | NULL         |    7300.33 |    401 |         1 |
+----+--------+--------+-----+------------+-----------------------------+--------------+------------+--------+-----------+
4 rows in set (0.00 sec)

mysql>

"""
分组之后 最小可操作单位应该是组 还不再是组内的单个数据
    上述命令在你没有设置严格模式的时候是可正常执行的 返回的是分组之后 每个组的第一条数据 但是这不符合分组的规范:分组之后不应该考虑单个数据 而应该以组为操作单位(分组之后 没办法直接获取组内单个数据)
    如果设置了严格模式 那么上述命令会直接报错 
"""
set global sql_mode = 'strict_trans_tables,only_full_group_by';
mysql> set global sql_mode ='strict_trans_tables,only_full_group_by';
Query OK, 0 rows affected (0.00 sec)
设置严格模式之后  分组 默认只能拿到分组的依据
select post from emp group by post;  
按照什么分组就只能拿到分组 其他字段不能直接获取 需要借助于一些方法(聚合函数)
mysql> select name from emp group by post;
ERROR 1055 (42000): 'day47.emp.name' isn't in GROUP BY
mysql>

"""
什么时候需要分组啊？？？
    关键字 
        每个 平均 最高 最低 
    
    聚合函数
        max
        min
        sum
        count
        avg
"""
# 1.获取每个部门的最高薪资
select post,max(salary) from emp group by post;
mysql> select post,max(salary) from emp group by post;
+-----------------------------+-------------+
| post                        | max(salary) |
+-----------------------------+-------------+
| 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>
select post as '部门',max(salary) as '最高薪资' from emp group by post;
mysql> select post as '部门',max(salary) as '最高薪资' from emp group by post;;
+-----------------------------+--------------+
| 部门                        | 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>
select post '部门',max(salary) '最高薪资' from emp group by post;
# as可以给字段起别名 也可以直接省略不写 但是不推荐 因为省略的话语意不明确 容易错乱

# 2.获取每个部门的最低薪资
select post,min(salary) from emp group by post;
mysql> select post,min(salary) from emp group by post;
+-----------------------------+-------------+
| post                        | min(salary) |
+-----------------------------+-------------+
| 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>
# 3.获取每个部门的平均薪资
select post,avg(salary) from emp group by post;
mysql> select post,avg(salary) from emp group by post;
+-----------------------------+---------------+
| post                        | avg(salary)   |
+-----------------------------+---------------+
| 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>
# 4.获取每个部门的工资总和
select post,sum(salary) from emp group by post;
# 5.获取每个部门的人数
select post,count(id) from emp group by post;  # 常用 符合逻辑
mysql> select post,count(id) from emp group by post;
+-----------------------------+-----------+
| post                        | count(id) |
+-----------------------------+-----------+
| operation                   |         5 |
| sale                        |         5 |
| teacher                     |         7 |
| 张江第一帅形象代言          |         1 |
+-----------------------------+-----------+
4 rows in set (0.00 sec)

mysql>
    
select post,count(salary) from emp group by post;
select post,count(age) from emp group by post;
select post,count(post_comment) from emp group by post;  null不行

# 6.查询分组之后的部门名称和每个部门下所有的员工姓名 
# group_concat不单单可以支持你获取分组之后的其他字段值 还支持拼接操作
select post,group_concat(name) from emp group by post;
mysql> select post,group_concat(name) from emp group by post;
+-----------------------------+------------------------------------------------+
| post                        | group_concat(name)                             |
+-----------------------------+------------------------------------------------+
| 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)
select post,group_concat(name,'_DSB') from emp group by post;
mysql> select post,group_concat(name,'_dsb') from emp group by post;
+-----------------------------+--------------------------------------------------------------------+
| post                        | group_concat(name,'_dsb')                                          |
+-----------------------------+--------------------------------------------------------------------+
| operation                   | 程咬铁_dsb,程咬铜_dsb,程咬银_dsb,程咬金_dsb,僧龙_dsb               |
| sale                        | 拉拉_dsb,乐乐_dsb,西西_dsb,呵呵_dsb,哈哈_dsb                       |
| teacher                     | sank_dsb,jenny_dsb,jack_dsb,owen_dsb,tony_dsb,kevin_dsb,tom_dsb    |
| 张江第一帅形象代言          | jason_dsb                                                          |
+-----------------------------+--------------------------------------------------------------------+
4 rows in set (0.00 sec)

select post,group_concat(name,':',salary) from emp group by post;
# concat不分组的时候用 
select concat('NAME:',name),concat('SAL:',salary) from emp;
mysql> select concat('名字：',name),concat('薪资：',salary) from emp;
+--------------------------+----------------------------+
| concat('名字：',name)    | concat('薪资：',salary)    |
+--------------------------+----------------------------+
| 名字：jason              | 薪资：7300.33              |
| 名字：tom                | 薪资：1000000.31           |
| 名字：kevin              | 薪资：8300.00              |
| 名字：tony               | 薪资：3500.00              |
| 名字：owen               | 薪资：2100.00              |
| 名字：jack               | 薪资：9000.00              |
| 名字：jenny              | 薪资：30000.00             |
| 名字：sank               | 薪资：10000.00             |
| 名字：哈哈               | 薪资：3000.13              |
| 名字：呵呵               | 薪资：2000.35              |
| 名字：西西               | 薪资：1000.37              |
| 名字：乐乐               | 薪资：3000.29              |
| 名字：拉拉               | 薪资：4000.33              |
| 名字：僧龙               | 薪资：10000.13             |
| 名字：程咬金             | 薪资：20000.00             |
| 名字：程咬银             | 薪资：19000.00             |
| 名字：程咬铜             | 薪资：18000.00             |
| 名字：程咬铁             | 薪资：17000.00             |
+--------------------------+----------------------------+
18 rows in set (0.00 sec)
# 补充 as语法不单单可以给字段起别名 还可以给表临时起别名
select emp.id,emp.name from emp;  
select emp.id,emp.name from emp as t1;   报错
select t1.id,t1.name from emp as t1;

# 查询每个人的年薪  12薪
select name,salary*12 from emp;
mysql> select name,salary*12 as '年薪'from emp;
+-----------+-------------+
| name      | 年薪        |
+-----------+-------------+
| jason     |    87603.96 |
| tom       | 12000003.72 |
| kevin     |    99600.00 |
| tony      |    42000.00 |
| owen      |    25200.00 |
| jack      |   108000.00 |
| jenny     |   360000.00 |
| sank      |   120000.00 |
| 哈哈      |    36001.56 |
| 呵呵      |    24004.20 |
| 西西      |    12004.44 |
| 乐乐      |    36003.48 |
| 拉拉      |    48003.96 |
| 僧龙      |   120001.56 |
| 程咬金    |   240000.00 |
| 程咬银    |   228000.00 |
| 程咬铜    |   216000.00 |
| 程咬铁    |   204000.00 |
+-----------+-------------+
18 rows in set (0.00 sec)

分组注意事项

# 关键字where和group by同时出现的时候group by必须在where的后面
where先对整体数据进行过滤之后再分组操作
where筛选条件不能使用聚合函数
select id,name,age from emp where max(salary) > 3000;

select max(salary) from emp;  # 不分组 默认整体就是一组

# 统计各部门年龄在30岁以上的员工平均薪资
    1 先求所有年龄大于30岁的员工
        select * from emp where age>30;
    2 再对结果进行分组
         select * from emp where age>30 group by post;
    
    select post,avg(salary) from emp where age>30 group by post;

having分组之后的筛选条件

"""
having的语法根where是一致的
只不过having是在分组之后进行的过滤操作
即having是可以直接使用聚合函数的
"""
# 统计各部门年龄在30岁以上的员工平均工资并且保留平均薪资大于10000的部门
select post,avg(salary) from emp 
        where age>30 
        group by post
        having avg(salary) > 10000
        ;

mysql> select post, avg(salary) from emp where age>30 group by post having avg(salary)>10000;
+---------+---------------+
| post    | avg(salary)   |
+---------+---------------+
| teacher | 255450.077500 |
+---------+---------------+
1 row in set (0.00 sec)

mysql>

distinct去重

"""
一定要注意 必须是完全一样的数据才可以去重！！！
一定不要将逐渐忽视了 有逐渐存在的情况下 是不可能去重的
[
{'id':1,'name':'jason','age':18},
{'id':2,'name':'jason','age':18},
{'id':3,'name':'egon','age':18}
]
ORM  对象关系映射   让不懂SQL语句的人也能够非常牛逼的操作数据库
表                                类
一条条的数据                        对象
字段对应的值                        对象的属性

你再写类 就意味着在创建表
用类生成对象 就意味着再创建数据
对象点属性 就是在获取数据字段对应的值
目的就是减轻python程序员的压力 只需要会python面向对象的知识点就可以操作MySQL
"""
select distinct id,age from emp;
select distinct age from emp;

mysql> select distinct id,age from emp;
+----+-----+
| id | age |
+----+-----+
|  1 |  18 |
|  2 |  78 |
|  3 |  81 |
|  4 |  73 |
|  5 |  28 |
|  6 |  18 |
|  7 |  18 |
|  8 |  48 |
|  9 |  48 |
| 10 |  38 |
| 11 |  18 |
| 12 |  18 |
| 13 |  28 |
| 14 |  28 |
| 15 |  18 |
| 16 |  18 |
| 17 |  18 |
| 18 |  18 |
+----+-----+
18 rows in set (0.00 sec)



mysql> select distinct age from emp;
+-----+
| age |
+-----+
|  18 |
|  78 |
|  81 |
|  73 |
|  28 |
|  48 |
|  38 |
+-----+
7 rows in set (0.00 sec)

mysql>

order by排序

select * from emp order by salary;
select * from emp order by salary asc;
select * from emp order by salary desc;

mysql> select * from emp order by salary;
+----+-----------+--------+-----+------------+-----------------------------+--------------+------------+--------+-----------+
| id | name      | sex    | age | hire_date  | post                        | post_comment | salary     | office | depart_id |
+----+-----------+--------+-----+------------+-----------------------------+--------------+------------+--------+-----------+
| 11 | 西西      | female |  18 | 2011-03-12 | sale                        | NULL         |    1000.37 |    402 |         2 |
| 10 | 呵呵      | female |  38 | 2010-11-01 | sale                        | NULL         |    2000.35 |    402 |         2 |
|  5 | owen      | male   |  28 | 2012-11-01 | teacher                     | NULL         |    2100.00 |    401 |         1 |
|  9 | 哈哈      | female |  48 | 2015-03-11 | sale                        | NULL         |    3000.13 |    402 |         2 |
| 12 | 乐乐      | female |  18 | 2016-05-13 | sale                        | NULL         |    3000.29 |    402 |         2 |
|  4 | tony      | male   |  73 | 2014-07-01 | teacher                     | NULL         |    3500.00 |    401 |         1 |
| 13 | 拉拉      | female |  28 | 2017-01-27 | sale                        | NULL         |    4000.33 |    402 |         2 |
|  1 | jason     | male   |  18 | 2017-03-01 | 张江第一帅形象代言          | NULL         |    7300.33 |    401 |         1 |
|  3 | kevin     | male   |  81 | 2013-03-05 | teacher                     | NULL         |    8300.00 |    401 |         1 |
|  6 | jack      | female |  18 | 2011-02-11 | teacher                     | NULL         |    9000.00 |    401 |         1 |
|  8 | sank      | male   |  48 | 2010-11-11 | teacher                     | NULL         |   10000.00 |    401 |         1 |
| 14 | 僧龙      | male   |  28 | 2016-03-11 | operation                   | NULL         |   10000.13 |    403 |         3 |
| 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 |
|  7 | jenny     | male   |  18 | 1900-03-01 | teacher                     | NULL         |   30000.00 |    401 |         1 |
|  2 | tom       | male   |  78 | 2015-03-02 | teacher                     | NULL         | 1000000.31 |    401 |         1 |
+----+-----------+--------+-----+------------+-----------------------------+--------------+------------+--------+-----------+
18 rows in set (0.00 sec)

mysql> select * from emp order by salary asc;
+----+-----------+--------+-----+------------+-----------------------------+--------------+------------+--------+-----------+
| id | name      | sex    | age | hire_date  | post                        | post_comment | salary     | office | depart_id |
+----+-----------+--------+-----+------------+-----------------------------+--------------+------------+--------+-----------+
| 11 | 西西      | female |  18 | 2011-03-12 | sale                        | NULL         |    1000.37 |    402 |         2 |
| 10 | 呵呵      | female |  38 | 2010-11-01 | sale                        | NULL         |    2000.35 |    402 |         2 |
|  5 | owen      | male   |  28 | 2012-11-01 | teacher                     | NULL         |    2100.00 |    401 |         1 |
|  9 | 哈哈      | female |  48 | 2015-03-11 | sale                        | NULL         |    3000.13 |    402 |         2 |
| 12 | 乐乐      | female |  18 | 2016-05-13 | sale                        | NULL         |    3000.29 |    402 |         2 |
|  4 | tony      | male   |  73 | 2014-07-01 | teacher                     | NULL         |    3500.00 |    401 |         1 |
| 13 | 拉拉      | female |  28 | 2017-01-27 | sale                        | NULL         |    4000.33 |    402 |         2 |
|  1 | jason     | male   |  18 | 2017-03-01 | 张江第一帅形象代言          | NULL         |    7300.33 |    401 |         1 |
|  3 | kevin     | male   |  81 | 2013-03-05 | teacher                     | NULL         |    8300.00 |    401 |         1 |
|  6 | jack      | female |  18 | 2011-02-11 | teacher                     | NULL         |    9000.00 |    401 |         1 |
|  8 | sank      | male   |  48 | 2010-11-11 | teacher                     | NULL         |   10000.00 |    401 |         1 |
| 14 | 僧龙      | male   |  28 | 2016-03-11 | operation                   | NULL         |   10000.13 |    403 |         3 |
| 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 |
|  7 | jenny     | male   |  18 | 1900-03-01 | teacher                     | NULL         |   30000.00 |    401 |         1 |
|  2 | tom       | male   |  78 | 2015-03-02 | teacher                     | NULL         | 1000000.31 |    401 |         1 |
+----+-----------+--------+-----+------------+-----------------------------+--------------+------------+--------+-----------+
18 rows in set (0.00 sec)

mysql> select *from emp order by salary desc;
+----+-----------+--------+-----+------------+-----------------------------+--------------+------------+--------+-----------+
| id | name      | sex    | age | hire_date  | post                        | post_comment | salary     | office | depart_id |
+----+-----------+--------+-----+------------+-----------------------------+--------------+------------+--------+-----------+
|  2 | tom       | male   |  78 | 2015-03-02 | teacher                     | NULL         | 1000000.31 |    401 |         1 |
|  7 | jenny     | male   |  18 | 1900-03-01 | teacher                     | NULL         |   30000.00 |    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 |
| 14 | 僧龙      | male   |  28 | 2016-03-11 | operation                   | NULL         |   10000.13 |    403 |         3 |
|  8 | sank      | male   |  48 | 2010-11-11 | teacher                     | NULL         |   10000.00 |    401 |         1 |
|  6 | jack      | female |  18 | 2011-02-11 | teacher                     | NULL         |    9000.00 |    401 |         1 |
|  3 | kevin     | male   |  81 | 2013-03-05 | teacher                     | NULL         |    8300.00 |    401 |         1 |
|  1 | jason     | male   |  18 | 2017-03-01 | 张江第一帅形象代言          | NULL         |    7300.33 |    401 |         1 |
| 13 | 拉拉      | female |  28 | 2017-01-27 | sale                        | NULL         |    4000.33 |    402 |         2 |
|  4 | tony      | male   |  73 | 2014-07-01 | teacher                     | NULL         |    3500.00 |    401 |         1 |
| 12 | 乐乐      | female |  18 | 2016-05-13 | sale                        | NULL         |    3000.29 |    402 |         2 |
|  9 | 哈哈      | female |  48 | 2015-03-11 | sale                        | NULL         |    3000.13 |    402 |         2 |
|  5 | owen      | male   |  28 | 2012-11-01 | teacher                     | NULL         |    2100.00 |    401 |         1 |
| 10 | 呵呵      | female |  38 | 2010-11-01 | sale                        | NULL         |    2000.35 |    402 |         2 |
| 11 | 西西      | female |  18 | 2011-03-12 | sale                        | NULL         |    1000.37 |    402 |         2 |
+----+-----------+--------+-----+------------+-----------------------------+--------------+------------+--------+-----------+
18 rows in set (0.00 sec)

mysql>
"""
order by默认是升序  asc 该asc可以省略不写
也可以修改为降序     desc
"""
select * from emp order by age desc,salary asc;

mysql> select *from emp order by age desc,salary;
+----+-----------+--------+-----+------------+-----------------------------+--------------+------------+--------+-----------+
| id | name      | sex    | age | hire_date  | post                        | post_comment | salary     | office | depart_id |
+----+-----------+--------+-----+------------+-----------------------------+--------------+------------+--------+-----------+
|  3 | kevin     | male   |  81 | 2013-03-05 | teacher                     | NULL         |    8300.00 |    401 |         1 |
|  2 | tom       | male   |  78 | 2015-03-02 | teacher                     | NULL         | 1000000.31 |    401 |         1 |
|  4 | tony      | male   |  73 | 2014-07-01 | teacher                     | NULL         |    3500.00 |    401 |         1 |
|  9 | 哈哈      | female |  48 | 2015-03-11 | sale                        | NULL         |    3000.13 |    402 |         2 |
|  8 | sank      | male   |  48 | 2010-11-11 | teacher                     | NULL         |   10000.00 |    401 |         1 |
| 10 | 呵呵      | female |  38 | 2010-11-01 | sale                        | NULL         |    2000.35 |    402 |         2 |
|  5 | owen      | male   |  28 | 2012-11-01 | teacher                     | NULL         |    2100.00 |    401 |         1 |
| 13 | 拉拉      | female |  28 | 2017-01-27 | sale                        | NULL         |    4000.33 |    402 |         2 |
| 14 | 僧龙      | male   |  28 | 2016-03-11 | operation                   | NULL         |   10000.13 |    403 |         3 |
| 11 | 西西      | female |  18 | 2011-03-12 | sale                        | NULL         |    1000.37 |    402 |         2 |
| 12 | 乐乐      | female |  18 | 2016-05-13 | sale                        | NULL         |    3000.29 |    402 |         2 |
|  1 | jason     | male   |  18 | 2017-03-01 | 张江第一帅形象代言          | NULL         |    7300.33 |    401 |         1 |
|  6 | jack      | female |  18 | 2011-02-11 | teacher                     | NULL         |    9000.00 |    401 |         1 |
| 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 |
|  7 | jenny     | male   |  18 | 1900-03-01 | teacher                     | NULL         |   30000.00 |    401 |         1 |
+----+-----------+--------+-----+------------+-----------------------------+--------------+------------+--------+-----------+
18 rows in set (0.00 sec)

mysql>
# 先按照age降序排  如果碰到age相同 则再按照salary升序排

# 统计各部门年龄在10岁以上的员工平均工资并且保留平均薪资大于1000的部门,然后对平均工资降序排序
    select post,avg(salary) from emp 
        where age>10 
        group by post
        having avg(salary) > 1000
        order by avg(salary) desc
        ;
mysql> select post,avg(salary) from emp
    -> where age >10
    -> group by post
    -> having avg(salary) >1000
    -> order by avg(salary) desc;
+-----------------------------+---------------+
| post                        | avg(salary)   |
+-----------------------------+---------------+
| teacher                     | 151842.901429 |
| operation                   |  16800.026000 |
| 张江第一帅形象代言          |   7300.330000 |
| sale                        |   2600.294000 |
+-----------------------------+---------------+
4 rows in set (0.00 sec)

mysql>

limit限制展示条数

select * from emp;
"""针对数据过多的情况 我们通常都是做分页处理"""
select * from emp limit 3;  # 只展示三条数据

mysql> select * from emp limit 3;
+----+-------+------+-----+------------+-----------------------------+--------------+------------+--------+-----------+
| id | name  | sex  | age | hire_date  | post                        | post_comment | salary     | office | depart_id |
+----+-------+------+-----+------------+-----------------------------+--------------+------------+--------+-----------+
|  1 | jason | male |  18 | 2017-03-01 | 张江第一帅形象代言          | NULL         |    7300.33 |    401 |         1 |
|  2 | tom   | male |  78 | 2015-03-02 | teacher                     | NULL         | 1000000.31 |    401 |         1 |
|  3 | kevin | male |  81 | 2013-03-05 | teacher                     | NULL         |    8300.00 |    401 |         1 |
+----+-------+------+-----+------------+-----------------------------+--------------+------------+--------+-----------+
3 rows in set (0.00 sec)

select * from emp limit 0,5;
select * from emp limit 5,5;

mysql> select * from emp limit 0,5;
+----+-------+------+-----+------------+-----------------------------+--------------+------------+--------+-----------+
| id | name  | sex  | age | hire_date  | post                        | post_comment | salary     | office | depart_id |
+----+-------+------+-----+------------+-----------------------------+--------------+------------+--------+-----------+
|  1 | jason | male |  18 | 2017-03-01 | 张江第一帅形象代言          | NULL         |    7300.33 |    401 |         1 |
|  2 | tom   | male |  78 | 2015-03-02 | teacher                     | NULL         | 1000000.31 |    401 |         1 |
|  3 | kevin | male |  81 | 2013-03-05 | teacher                     | NULL         |    8300.00 |    401 |         1 |
|  4 | tony  | male |  73 | 2014-07-01 | teacher                     | NULL         |    3500.00 |    401 |         1 |
|  5 | owen  | male |  28 | 2012-11-01 | teacher                     | NULL         |    2100.00 |    401 |         1 |
+----+-------+------+-----+------------+-----------------------------+--------------+------------+--------+-----------+
5 rows in set (0.00 sec)

mysql> select * from emp limit 5,5;
+----+--------+--------+-----+------------+---------+--------------+----------+--------+-----------+
| id | name   | sex    | age | hire_date  | post    | post_comment | salary   | office | depart_id |
+----+--------+--------+-----+------------+---------+--------------+----------+--------+-----------+
|  6 | jack   | female |  18 | 2011-02-11 | teacher | NULL         |  9000.00 |    401 |         1 |
|  7 | jenny  | male   |  18 | 1900-03-01 | teacher | NULL         | 30000.00 |    401 |         1 |
|  8 | sank   | male   |  48 | 2010-11-11 | teacher | NULL         | 10000.00 |    401 |         1 |
|  9 | 哈哈   | female |  48 | 2015-03-11 | sale    | NULL         |  3000.13 |    402 |         2 |
| 10 | 呵呵   | female |  38 | 2010-11-01 | sale    | NULL         |  2000.35 |    402 |         2 |
+----+--------+--------+-----+------------+---------+--------------+----------+--------+-----------+
5 rows in set (0.00 sec)

mysql>
第一个参数是起始位置
第二个参数是展示条数

正则

select * from emp where name regexp '^j.*(n|y)$';
查找emp表中名字符合 j开头，n或者y结尾的 信息
mysql> select * from emp where name regexp '^j.*(n|y)$';
+----+-------+------+-----+------------+-----------------------------+--------------+----------+--------+-----------+
| id | name  | sex  | age | hire_date  | post                        | post_comment | salary   | office | depart_id |
+----+-------+------+-----+------------+-----------------------------+--------------+----------+--------+-----------+
|  1 | jason | male |  18 | 2017-03-01 | 张江第一帅形象代言          | NULL         |  7300.33 |    401 |         1 |
|  7 | jenny | male |  18 | 1900-03-01 | teacher                     | NULL         | 30000.00 |    401 |         1 |
+----+-------+------+-----+------------+-----------------------------+--------------+----------+--------+-----------+
2 rows in set (0.00 sec)

mysql>

多表操作

前期表准备

#建表
create table dep(
id int,
name varchar(20) 
);

create table emp(
id int primary key auto_increment,
name varchar(20),
sex enum('male','female') not null default 'male',
age int,
dep_id int
);

#插入数据
insert into dep values
(200,'技术'),
(201,'人力资源'),
(202,'销售'),
(203,'运营');

insert into emp(name,sex,age,dep_id) values
('jason','male',18,200),
('egon','female',48,201),
('kevin','male',18,201),
('nick','male',28,202),
('owen','male',18,203),
('jerry','female',18,204);

表查询

select * from dep,emp;  # 结果   笛卡尔积
"""
了解即可 不知道也没关系
"""

select * from emp,dep where emp.dep_id = dep.id;

"""
MySQL也知道 你在后面查询数据过程中 肯定会经常用到拼表操作 
所以特地给你开设了对应的方法
    inner join  内连接
    left join   左连接
    right join  右连接
    union        全连接
"""
# inner join  内连接
select * from emp inner join dep on emp.dep_id = dep.id;
# 只拼接两张表中公有的数据部分

# left join   左连接
select * from emp left join dep on emp.dep_id = dep.id;
# 左表所有的数据都展示出来 没有对应的项就用NULL

# right join  右连接
select * from emp right join dep on emp.dep_id = dep.id;
# 右表所有的数据都展示出来 没有对应的项就用NULL

# union        全连接  左右两表所有的数据都展示出来
select * from emp left join dep on emp.dep_id = dep.id
union
select * from emp right join dep on emp.dep_id = dep.id;

子查询

"""
子查询就是我们平时解决问题的思路
    分步骤解决问题
        第一步
        第二步
        ...
将一个查询语句的结果当做另外一个查询语句的条件去用
"""
# 查询部门是技术或者人力资源的员工信息
    1 先获取部门的id号
    2 再去员工表里面筛选出对应的员工
    select id from dep where name='技术' or name = '人力资源';
    
    select name from emp where dep_id in (200,201);
    
    
    select * from emp where dep_id in (select id from dep where name='技术' or name = '人力资源');

总结

表的查询结果可以作为其他表的查询条件
也可以通过起别名的方式把它作为一个张虚拟表根其他表关联

"""
多表查询就两种方式
先拼接表再查询
子查询 一步一步来
"""