day40 增删改 单表查询的语法与关键字的执行优先级 简单查询,where关键字,group by关键字,having关键字,order by关键字,limit关键字,正则表达式,多表连接,子查询,查询语句的执行优先级

增删改

egon上课笔记

mysql> show databases;
+--------------------+
| Database           |
+--------------------+
| information_schema |
| db1                |
| mysql              |
| performance_schema |
| sb1                |
| sb2                |
| sb3                |
| test               |
+--------------------+
8 rows in set (0.00 sec)

mysql> create database sb4;
Query OK, 1 row affected (0.00 sec)

mysql> use sb4;
Database changed
mysql> desc mysql.user;
+------------------------+-----------------------------------+------+-----+-----
------------------+-------+
| Field                  | Type                              | Null | Key | Defa
ult               | Extra |
+------------------------+-----------------------------------+------+-----+-----
------------------+-------+
| Host                   | char(60)                          | NO   | PRI |
                  |       |
| User                   | char(16)                          | NO   | PRI |
                  |       |
| Password               | char(41)                          | NO   |     |
                  |       |
| Select_priv            | enum('N','Y')                     | NO   |     | N
                  |       |
| Insert_priv            | enum('N','Y')                     | NO   |     | N
                  |       |
| Update_priv            | enum('N','Y')                     | NO   |     | N
                  |       |
| Delete_priv            | enum('N','Y')                     | NO   |     | N
                  |       |
| Create_priv            | enum('N','Y')                     | NO   |     | N
                  |       |
| Drop_priv              | enum('N','Y')                     | NO   |     | N
                  |       |
| Reload_priv            | enum('N','Y')                     | NO   |     | N
                  |       |
| Shutdown_priv          | enum('N','Y')                     | NO   |     | N
                  |       |
| Process_priv           | enum('N','Y')                     | NO   |     | N
                  |       |
| File_priv              | enum('N','Y')                     | NO   |     | N
                  |       |
| Grant_priv             | enum('N','Y')                     | NO   |     | N
                  |       |
| References_priv        | enum('N','Y')                     | NO   |     | N
                  |       |
| Index_priv             | enum('N','Y')                     | NO   |     | N
                  |       |
| Alter_priv             | enum('N','Y')                     | NO   |     | N
                  |       |
| Show_db_priv           | enum('N','Y')                     | NO   |     | N
                  |       |
| Super_priv             | enum('N','Y')                     | NO   |     | N
                  |       |
| Create_tmp_table_priv  | enum('N','Y')                     | NO   |     | N
                  |       |
| Lock_tables_priv       | enum('N','Y')                     | NO   |     | N
                  |       |
| Execute_priv           | enum('N','Y')                     | NO   |     | N
                  |       |
| Repl_slave_priv        | enum('N','Y')                     | NO   |     | N
                  |       |
| Repl_client_priv       | enum('N','Y')                     | NO   |     | N
                  |       |
| Create_view_priv       | enum('N','Y')                     | NO   |     | N
                  |       |
| Show_view_priv         | enum('N','Y')                     | NO   |     | N
                  |       |
| Create_routine_priv    | enum('N','Y')                     | NO   |     | N
                  |       |
| Alter_routine_priv     | enum('N','Y')                     | NO   |     | N
                  |       |
| Create_user_priv       | enum('N','Y')                     | NO   |     | N
                  |       |
| Event_priv             | enum('N','Y')                     | NO   |     | N
                  |       |
| Trigger_priv           | enum('N','Y')                     | NO   |     | N
                  |       |
| Create_tablespace_priv | enum('N','Y')                     | NO   |     | N
                  |       |
| ssl_type               | enum('','ANY','X509','SPECIFIED') | NO   |     |
                  |       |
| ssl_cipher             | blob                              | NO   |     | NULL
                  |       |
| x509_issuer            | blob                              | NO   |     | NULL
                  |       |
| x509_subject           | blob                              | NO   |     | NULL
                  |       |
| max_questions          | int(11) unsigned                  | NO   |     | 0
                  |       |
| max_updates            | int(11) unsigned                  | NO   |     | 0
                  |       |
| max_connections        | int(11) unsigned                  | NO   |     | 0
                  |       |
| max_user_connections   | int(11) unsigned                  | NO   |     | 0
                  |       |
| plugin                 | char(64)                          | YES  |     | mysq
l_native_password |       |
| authentication_string  | text                              | YES  |     | NULL
                  |       |
| password_expired       | enum('N','Y')                     | NO   |     | N
                  |       |
+------------------------+-----------------------------------+------+-----+-----
------------------+-------+
43 rows in set (0.01 sec)

mysql> create table user(host char(60),user char(16),password char(41));
Query OK, 0 rows affected (0.02 sec)

mysql> desc user;
+----------+----------+------+-----+---------+-------+
| Field    | Type     | Null | Key | Default | Extra |
+----------+----------+------+-----+---------+-------+
| host     | char(60) | YES  |     | NULL    |       |
| user     | char(16) | YES  |     | NULL    |       |
| password | char(41) | YES  |     | NULL    |       |
+----------+----------+------+-----+---------+-------+
3 rows in set (0.04 sec)

mysql> select host,user,password from mysql.user;
+-----------+------+----------+
| host      | user | password |
+-----------+------+----------+
| localhost | root |          |
| 127.0.0.1 | root |          |
| ::1       | root |          |
| localhost |      |          |
+-----------+------+----------+
4 rows in set (0.00 sec)

mysql> insert into user select host,user,password from mysql.user;
Query OK, 4 rows affected (0.01 sec)
Records: 4  Duplicates: 0  Warnings: 0

mysql> select*from user;
+-----------+------+----------+
| host      | user | password |
+-----------+------+----------+
| localhost | root |          |
| 127.0.0.1 | root |          |
| ::1       | root |          |
| localhost |      |          |
+-----------+------+----------+
4 rows in set (0.00 sec)

mysql> select*from user;
+-----------+------+----------+
| host      | user | password |
+-----------+------+----------+
| localhost | root |          |
| 127.0.0.1 | root |          |
| ::1       | root |          |
| localhost |      |          |
+-----------+------+----------+
4 rows in set (0.00 sec)

mysql> update user set user="ROOT" where host="localhost";
Query OK, 2 rows affected (0.01 sec)
Rows matched: 2  Changed: 2  Warnings: 0

mysql> select*from user;
+-----------+------+----------+
| host      | user | password |
+-----------+------+----------+
| localhost | ROOT |          |
| 127.0.0.1 | root |          |
| ::1       | root |          |
| localhost | ROOT |          |
+-----------+------+----------+
4 rows in set (0.00 sec)

mysql> delete from user where user="ROOT";
Query OK, 4 rows affected (0.00 sec)

mysql> select*from user;
Empty set (0.00 sec)

mysql> create table t5(id int);
Query OK, 0 rows affected (0.02 sec)

mysql> insert into t5 values(1),(2),(3),(4);
Query OK, 4 rows affected (0.01 sec)
Records: 4  Duplicates: 0  Warnings: 0

mysql> select*from t5;
+------+
| id   |
+------+
|    1 |
|    2 |
|    3 |
|    4 |
+------+
4 rows in set (0.00 sec)

mysql> delete from t5 where id>2;
Query OK, 2 rows affected (0.00 sec)

mysql> delete from t5 where id>2;
Query OK, 0 rows affected (0.00 sec)

mysql> select*from t5;
+------+
| id   |
+------+
|    1 |
|    2 |
+------+
2 rows in set (0.00 sec)

column name 代表字段的意思

# 1、跟权限有关的几张表
user->db->table_priv->columns_priv

# 2、只创建账号
#create user tom@"客户端的ip" identified by "123";
create user tom@"192.168.15.%" identified by "123";
create user tom@"%" identified by "123";

#客户端：192.168.15.13               服务端：192.168.15.90

create user tom@"192.168.15.13 " identified by "123";
mysql -utom -p"123" -h 192.168.15.90 -P 3306

# 3、创建账号并且授权（只有root账号才能为其他账号授权grant）
# *.* ===> mysql.user
grant all on *.* to "tom"@"192.168.15.90" identified by "123";#all代表除了grant以外的所有权限

# db1.* ===> mysql.db
grant all on db1.* to "jack"@"192.168.15.90" identified by "123";#all代表除了grant以外的所有权限

# db1.t1 ===> mysql.tables_priv
grant all on db1.t1 to "rose"@"192.168.15.90" identified by "123";#all代表除了grant以外的所有权限

# db1.t1(id) ===> mysql.columns_priv
grant select(id),update(name) on db1.t1 to "lili"@"192.168.15.90" identified by "123";


# 修改完权限一定要
flush privileges;


drop user "tom"@"192.168.15.90";
drop user "jack"@"192.168.15.90";
drop user "rose"@"192.168.15.90";
drop user "lili"@"192.168.15.90";
flush privileges;

如何创建账号,以及具体步骤

增删改 视频有32分钟到结束

=============================================================================================================

03 单表查询的语法与关键字的执行优先级

#1、完整语法(语法级别关键字的排列顺序如下)
select distinct 字段1,字段2,字段3,... from 库名.表名   #distinct去重的意思
                    where 约束条件
                    group by 分组依据
                    having 过滤条件
                    order by 排序的字段
                    limit 限制显示的条数
                    ;
# 必须要有的关键字如下：
select * from t1;


# 关键字执行的优先级
from
where
group by
having
distinct
order by
limit


def from():
    pass

def where():
    pass

def group():
    pass

def having():
    pass

def distinct():
    pass

def order():
    pass

def limit():
    pass

def select():
    f=from()
    res1=where(f)
    res2=group(res1)
    res3=having(res2)
    res4=distinct(res3)
    res5=order(res4)
    limit(res5)

 where关键字

2、where
select * from emp where id >= 10 and id <=15; # 等同于select * from emp where id between 10 and 15;
select * from emp where id = 6 or id = 9 or id = 12; # 等同于select * from emp where id in (6,9,12);

_代表任意单个字符
%代表任意无穷个字符
select * from emp where name like "__";
select * from emp where name like "jin%";
select * from emp where id not in (6,9,12);
select * from emp where id not between 10 and 15;

egon上机笔记

----------+------------+
| id | name       | sex    | age | hire_date  | post                       | pos
t_comment | salary     |
+----+------------+--------+-----+------------+----------------------------+----
----------+------------+
|  1 | egon       | male   |  18 | 2017-03-01 | 老男孩驻沙河办事处外交大使 | NUL
L         |    7300.33 |
|  2 | alex       | male   |  78 | 2015-03-02 | teacher                    | NUL
L         | 1000000.31 |
|  3 | wupeiqi    | male   |  81 | 2013-03-05 | teacher                    | NUL
L         |    8300.00 |
|  4 | yuanhao    | male   |  73 | 2014-07-01 | teacher                    | NUL
L         |    3500.00 |
|  5 | liwenzhou  | male   |  28 | 2012-11-01 | teacher                    | NUL
L         |    2100.00 |
|  6 | jingliyang | female |  18 | 2011-02-11 | teacher                    | NUL
L         |    9000.00 |
|  7 | jinxin     | male   |  18 | 1900-03-01 | teacher                    | NUL
L         |   30000.00 |
|  8 | 成龙       | male   |  48 | 2010-11-11 | teacher                    | NUL
L         |   10000.00 |
|  9 | 歪歪       | female |  48 | 2015-03-11 | sale                       | NUL
L         |    3000.13 |
| 10 | 丫丫       | female |  38 | 2010-11-01 | sale                       | NUL
L         |    2000.35 |
| 11 | 丁丁       | female |  18 | 2011-03-12 | sale                       | NUL
L         |    1000.37 |
| 12 | 星星       | female |  18 | 2016-05-13 | sale                       | NUL
L         |    3000.29 |
| 13 | 格格       | female |  28 | 2017-01-27 | sale                       | NUL
L         |    4000.33 |
| 14 | 张野       | male   |  28 | 2016-03-11 | operation                  | NUL
L         |   10000.13 |
| 15 | 程咬金     | male   |  18 | 1997-03-12 | operation                  | NUL
L         |   20000.00 |
| 16 | 程咬银     | female |  18 | 2013-03-11 | operation                  | NUL
L         |   19000.00 |
| 17 | 程咬铜     | male   |  18 | 2015-04-11 | operation                  | NUL
L         |   18000.00 |
| 18 | 程咬铁     | female |  18 | 2014-05-12 | operation                  | NUL
L         |   17000.00 |
+----+------------+--------+-----+------------+----------------------------+----
----------+------------+
18 rows in set (0.01 sec)

mysql> select*from emp where id>10 and id<15;
+----+------+--------+-----+------------+-----------+--------------+----------+
| id | name | sex    | age | hire_date  | post      | post_comment | salary   |
+----+------+--------+-----+------------+-----------+--------------+----------+
| 11 | 丁丁 | female |  18 | 2011-03-12 | sale      | NULL         |  1000.37 |
| 12 | 星星 | female |  18 | 2016-05-13 | sale      | NULL         |  3000.29 |
| 13 | 格格 | female |  28 | 2017-01-27 | sale      | NULL         |  4000.33 |
| 14 | 张野 | male   |  28 | 2016-03-11 | operation | NULL         | 10000.13 |
+----+------+--------+-----+------------+-----------+--------------+----------+
4 rows in set (0.00 sec)

mysql> select*from emp where id=10 and id=15;
Empty set (0.00 sec)

mysql> select*from emp where id between 10 and 15;
+----+--------+--------+-----+------------+-----------+--------------+----------
+
| id | name   | sex    | age | hire_date  | post      | post_comment | salary
|
+----+--------+--------+-----+------------+-----------+--------------+----------
+
| 10 | 丫丫   | female |  38 | 2010-11-01 | sale      | NULL         |  2000.35
|
| 11 | 丁丁   | female |  18 | 2011-03-12 | sale      | NULL         |  1000.37
|
| 12 | 星星   | female |  18 | 2016-05-13 | sale      | NULL         |  3000.29
|
| 13 | 格格   | female |  28 | 2017-01-27 | sale      | NULL         |  4000.33
|
| 14 | 张野   | male   |  28 | 2016-03-11 | operation | NULL         | 10000.13
|
| 15 | 程咬金 | male   |  18 | 1997-03-12 | operation | NULL         | 20000.00
|
+----+--------+--------+-----+------------+-----------+--------------+----------
+
6 rows in set (0.00 sec)

mysql> select*from emp;
+----+------------+--------+-----+------------+----------------------------+----
----------+------------+
| id | name       | sex    | age | hire_date  | post                       | pos
t_comment | salary     |
+----+------------+--------+-----+------------+----------------------------+----
----------+------------+
|  1 | egon       | male   |  18 | 2017-03-01 | 老男孩驻沙河办事处外交大使 | NUL
L         |    7300.33 |
|  2 | alex       | male   |  78 | 2015-03-02 | teacher                    | NUL
L         | 1000000.31 |
|  3 | wupeiqi    | male   |  81 | 2013-03-05 | teacher                    | NUL
L         |    8300.00 |
|  4 | yuanhao    | male   |  73 | 2014-07-01 | teacher                    | NUL
L         |    3500.00 |
|  5 | liwenzhou  | male   |  28 | 2012-11-01 | teacher                    | NUL
L         |    2100.00 |
|  6 | jingliyang | female |  18 | 2011-02-11 | teacher                    | NUL
L         |    9000.00 |
|  7 | jinxin     | male   |  18 | 1900-03-01 | teacher                    | NUL
L         |   30000.00 |
|  8 | 成龙       | male   |  48 | 2010-11-11 | teacher                    | NUL
L         |   10000.00 |
|  9 | 歪歪       | female |  48 | 2015-03-11 | sale                       | NUL
L         |    3000.13 |
| 10 | 丫丫       | female |  38 | 2010-11-01 | sale                       | NUL
L         |    2000.35 |
| 11 | 丁丁       | female |  18 | 2011-03-12 | sale                       | NUL
L         |    1000.37 |
| 12 | 星星       | female |  18 | 2016-05-13 | sale                       | NUL
L         |    3000.29 |
| 13 | 格格       | female |  28 | 2017-01-27 | sale                       | NUL
L         |    4000.33 |
| 14 | 张野       | male   |  28 | 2016-03-11 | operation                  | NUL
L         |   10000.13 |
| 15 | 程咬金     | male   |  18 | 1997-03-12 | operation                  | NUL
L         |   20000.00 |
| 16 | 程咬银     | female |  18 | 2013-03-11 | operation                  | NUL
L         |   19000.00 |
| 17 | 程咬铜     | male   |  18 | 2015-04-11 | operation                  | NUL
L         |   18000.00 |
| 18 | 程咬铁     | female |  18 | 2014-05-12 | operation                  | NUL
L         |   17000.00 |
+----+------------+--------+-----+------------+----------------------------+----
----------+------------+
18 rows in set (0.00 sec)

mysql> select*from emp where id>10;
+----+--------+--------+-----+------------+-----------+--------------+----------
+
| id | name   | sex    | age | hire_date  | post      | post_comment | salary
|
+----+--------+--------+-----+------------+-----------+--------------+----------
+
| 11 | 丁丁   | female |  18 | 2011-03-12 | sale      | NULL         |  1000.37
|
| 12 | 星星   | female |  18 | 2016-05-13 | sale      | NULL         |  3000.29
|
| 13 | 格格   | female |  28 | 2017-01-27 | sale      | NULL         |  4000.33
|
| 14 | 张野   | male   |  28 | 2016-03-11 | operation | NULL         | 10000.13
|
| 15 | 程咬金 | male   |  18 | 1997-03-12 | operation | NULL         | 20000.00
|
| 16 | 程咬银 | female |  18 | 2013-03-11 | operation | NULL         | 19000.00
|
| 17 | 程咬铜 | male   |  18 | 2015-04-11 | operation | NULL         | 18000.00
|
| 18 | 程咬铁 | female |  18 | 2014-05-12 | operation | NULL         | 17000.00
|
+----+--------+--------+-----+------------+-----------+--------------+----------
+
8 rows in set (0.00 sec)

mysql> select*from emp where id=6 or id=9 or id=12;
+----+------------+--------+-----+------------+---------+--------------+--------
-+
| id | name       | sex    | age | hire_date  | post    | post_comment | salary
 |
+----+------------+--------+-----+------------+---------+--------------+--------
-+
|  6 | jingliyang | female |  18 | 2011-02-11 | teacher | NULL         | 9000.00
 |
|  9 | 歪歪       | female |  48 | 2015-03-11 | sale    | NULL         | 3000.13
 |
| 12 | 星星       | female |  18 | 2016-05-13 | sale    | NULL         | 3000.29
 |
+----+------------+--------+-----+------------+---------+--------------+--------
-+
3 rows in set (0.00 sec)

mysql> select*from emp;
+----+------------+--------+-----+------------+----------------------------+----
----------+------------+
| id | name       | sex    | age | hire_date  | post                       | pos
t_comment | salary     |
+----+------------+--------+-----+------------+----------------------------+----
----------+------------+
|  1 | egon       | male   |  18 | 2017-03-01 | 老男孩驻沙河办事处外交大使 | NUL
L         |    7300.33 |
|  2 | alex       | male   |  78 | 2015-03-02 | teacher                    | NUL
L         | 1000000.31 |
|  3 | wupeiqi    | male   |  81 | 2013-03-05 | teacher                    | NUL
L         |    8300.00 |
|  4 | yuanhao    | male   |  73 | 2014-07-01 | teacher                    | NUL
L         |    3500.00 |
|  5 | liwenzhou  | male   |  28 | 2012-11-01 | teacher                    | NUL
L         |    2100.00 |
|  6 | jingliyang | female |  18 | 2011-02-11 | teacher                    | NUL
L         |    9000.00 |
|  7 | jinxin     | male   |  18 | 1900-03-01 | teacher                    | NUL
L         |   30000.00 |
|  8 | 成龙       | male   |  48 | 2010-11-11 | teacher                    | NUL
L         |   10000.00 |
|  9 | 歪歪       | female |  48 | 2015-03-11 | sale                       | NUL
L         |    3000.13 |
| 10 | 丫丫       | female |  38 | 2010-11-01 | sale                       | NUL
L         |    2000.35 |
| 11 | 丁丁       | female |  18 | 2011-03-12 | sale                       | NUL
L         |    1000.37 |
| 12 | 星星       | female |  18 | 2016-05-13 | sale                       | NUL
L         |    3000.29 |
| 13 | 格格       | female |  28 | 2017-01-27 | sale                       | NUL
L         |    4000.33 |
| 14 | 张野       | male   |  28 | 2016-03-11 | operation                  | NUL
L         |   10000.13 |
| 15 | 程咬金     | male   |  18 | 1997-03-12 | operation                  | NUL
L         |   20000.00 |
| 16 | 程咬银     | female |  18 | 2013-03-11 | operation                  | NUL
L         |   19000.00 |
| 17 | 程咬铜     | male   |  18 | 2015-04-11 | operation                  | NUL
L         |   18000.00 |
| 18 | 程咬铁     | female |  18 | 2014-05-12 | operation                  | NUL
L         |   17000.00 |
+----+------------+--------+-----+------------+----------------------------+----
----------+------------+
18 rows in set (0.00 sec)

mysql> select*from emp where name like "__";
+----+------+--------+-----+------------+-----------+--------------+----------+
| id | name | sex    | age | hire_date  | post      | post_comment | salary   |
+----+------+--------+-----+------------+-----------+--------------+----------+
|  8 | 成龙 | male   |  48 | 2010-11-11 | teacher   | NULL         | 10000.00 |
|  9 | 歪歪 | female |  48 | 2015-03-11 | sale      | NULL         |  3000.13 |
| 10 | 丫丫 | female |  38 | 2010-11-01 | sale      | NULL         |  2000.35 |
| 11 | 丁丁 | female |  18 | 2011-03-12 | sale      | NULL         |  1000.37 |
| 12 | 星星 | female |  18 | 2016-05-13 | sale      | NULL         |  3000.29 |
| 13 | 格格 | female |  28 | 2017-01-27 | sale      | NULL         |  4000.33 |
| 14 | 张野 | male   |  28 | 2016-03-11 | operation | NULL         | 10000.13 |
+----+------+--------+-----+------------+-----------+--------------+----------+
7 rows in set (0.00 sec)

mysql> select*from emp where name like "jin%";
+----+------------+--------+-----+------------+---------+--------------+--------
--+
| id | name       | sex    | age | hire_date  | post    | post_comment | salary
  |
+----+------------+--------+-----+------------+---------+--------------+--------
--+
|  6 | jingliyang | female |  18 | 2011-02-11 | teacher | NULL         |  9000.0
0 |
|  7 | jinxin     | male   |  18 | 1900-03-01 | teacher | NULL         | 30000.0
0 |
+----+------------+--------+-----+------------+---------+--------------+--------
--+
2 rows in set (0.00 sec)

mysql> select*from emp where id not between 10 and 15;
+----+------------+--------+-----+------------+----------------------------+----
----------+------------+
| id | name       | sex    | age | hire_date  | post                       | pos
t_comment | salary     |
+----+------------+--------+-----+------------+----------------------------+----
----------+------------+
|  1 | egon       | male   |  18 | 2017-03-01 | 老男孩驻沙河办事处外交大使 | NUL
L         |    7300.33 |
|  2 | alex       | male   |  78 | 2015-03-02 | teacher                    | NUL
L         | 1000000.31 |
|  3 | wupeiqi    | male   |  81 | 2013-03-05 | teacher                    | NUL
L         |    8300.00 |
|  4 | yuanhao    | male   |  73 | 2014-07-01 | teacher                    | NUL
L         |    3500.00 |
|  5 | liwenzhou  | male   |  28 | 2012-11-01 | teacher                    | NUL
L         |    2100.00 |
|  6 | jingliyang | female |  18 | 2011-02-11 | teacher                    | NUL
L         |    9000.00 |
|  7 | jinxin     | male   |  18 | 1900-03-01 | teacher                    | NUL
L         |   30000.00 |
|  8 | 成龙       | male   |  48 | 2010-11-11 | teacher                    | NUL
L         |   10000.00 |
|  9 | 歪歪       | female |  48 | 2015-03-11 | sale                       | NUL
L         |    3000.13 |
| 16 | 程咬银     | female |  18 | 2013-03-11 | operation                  | NUL
L         |   19000.00 |
| 17 | 程咬铜     | male   |  18 | 2015-04-11 | operation                  | NUL
L         |   18000.00 |
| 18 | 程咬铁     | female |  18 | 2014-05-12 | operation                  | NUL
L         |   17000.00 |
+----+------------+--------+-----+------------+----------------------------+----
----------+------------+
12 rows in set (0.00 sec)

3、group by分组
 什么分组：按照所有记录相同的部分进行归类，一定区分度低的字段
 为何要分组：当我们要以组为单位进行统计时就必须分组，分组的目的是为了以组为单位进行统计的，再去考虑单条记录毫无意义


 set global sql_mode="strict_trans_tables,only_full_group_by";
 注意:分组之后，只能查到分组的字段以及组内多条记录聚合的成果
select * from emp group by post;

 聚合函数
max
min
avg
sum
count


select post,count(id) from emp group by post;
select post,max(salary) from emp group by post;
select post,avg(salary) from emp group by post;
select sex,count(sex) from emp group by sex;

 统计出每个部门年龄30以上的员工的平均薪资
select post,avg(salary) from emp where age >= 30 group by post;

 注意：分组是在where之后发生的
mysql> select * from emp where max(salary) > 3000;
ERROR 1111 (HY000): Invalid use of group function

 group_concat

egon上机笔记

mysql> select*from emp group by post;
+----+------+--------+-----+------------+----------------------------+----------
----+------------+
| id | name | sex    | age | hire_date  | post                       | post_comm
ent | salary     |
+----+------+--------+-----+------------+----------------------------+----------
----+------------+
| 14 | 张野 | male   |  28 | 2016-03-11 | operation                  | NULL
    |   10000.13 |
|  9 | 歪歪 | female |  48 | 2015-03-11 | sale                       | NULL
    |    3000.13 |
|  2 | alex | male   |  78 | 2015-03-02 | teacher                    | NULL
    | 1000000.31 |
|  1 | egon | male   |  18 | 2017-03-01 | 老男孩驻沙河办事处外交大使 | NULL
    |    7300.33 |
+----+------+--------+-----+------------+----------------------------+----------
----+------------+
4 rows in set (0.00 sec)

mysql> select*from emp;
+----+------------+--------+-----+------------+----------------------------+----
----------+------------+
| id | name       | sex    | age | hire_date  | post                       | pos
t_comment | salary     |
+----+------------+--------+-----+------------+----------------------------+----
----------+------------+
|  1 | egon       | male   |  18 | 2017-03-01 | 老男孩驻沙河办事处外交大使 | NUL
L         |    7300.33 |
|  2 | alex       | male   |  78 | 2015-03-02 | teacher                    | NUL
L         | 1000000.31 |
|  3 | wupeiqi    | male   |  81 | 2013-03-05 | teacher                    | NUL
L         |    8300.00 |
|  4 | yuanhao    | male   |  73 | 2014-07-01 | teacher                    | NUL
L         |    3500.00 |
|  5 | liwenzhou  | male   |  28 | 2012-11-01 | teacher                    | NUL
L         |    2100.00 |
|  6 | jingliyang | female |  18 | 2011-02-11 | teacher                    | NUL
L         |    9000.00 |
|  7 | jinxin     | male   |  18 | 1900-03-01 | teacher                    | NUL
L         |   30000.00 |
|  8 | 成龙       | male   |  48 | 2010-11-11 | teacher                    | NUL
L         |   10000.00 |
|  9 | 歪歪       | female |  48 | 2015-03-11 | sale                       | NUL
L         |    3000.13 |
| 10 | 丫丫       | female |  38 | 2010-11-01 | sale                       | NUL
L         |    2000.35 |
| 11 | 丁丁       | female |  18 | 2011-03-12 | sale                       | NUL
L         |    1000.37 |
| 12 | 星星       | female |  18 | 2016-05-13 | sale                       | NUL
L         |    3000.29 |
| 13 | 格格       | female |  28 | 2017-01-27 | sale                       | NUL
L         |    4000.33 |
| 14 | 张野       | male   |  28 | 2016-03-11 | operation                  | NUL
L         |   10000.13 |
| 15 | 程咬金     | male   |  18 | 1997-03-12 | operation                  | NUL
L         |   20000.00 |
| 16 | 程咬银     | female |  18 | 2013-03-11 | operation                  | NUL
L         |   19000.00 |
| 17 | 程咬铜     | male   |  18 | 2015-04-11 | operation                  | NUL
L         |   18000.00 |
| 18 | 程咬铁     | female |  18 | 2014-05-12 | operation                  | NUL
L         |   17000.00 |
+----+------------+--------+-----+------------+----------------------------+----
----------+------------+
18 rows in set (0.00 sec)

mysql> select @@sql_mode;
+------------------------+
| @@sql_mode             |
+------------------------+
| NO_ENGINE_SUBSTITUTION |
+------------------------+
1 row in set (0.00 sec)

写sql语句的时候只能按照严格模式
mysql> set global sql_mode="strict_trans_tables,only_full_group_by";
Query OK, 0 rows affected (0.00 sec) #只能取分组的字段和聚合的结果

mysql> use sb5;
Database changed
mysql> select*from emp group by post;
ERROR 1055 (42000): 'sb5.emp.id' isn't in GROUP BY
mysql> select post from emp group by post;
+----------------------------+
| post                       |
+----------------------------+
| operation                  |
| sale                       |
| teacher                    |
| 老男孩驻沙河办事处外交大使 |
+----------------------------+
4 rows in set (0.00 sec)

# 聚合函数(切记分组以后才能用聚合函数)
max
min
avg
sum
count

mysql> select post from emp group by post;
+----------------------------+
| post                       |
+----------------------------+
| operation                  |
| sale                       |
| teacher                    |
| 老男孩驻沙河办事处外交大使 |
+----------------------------+
4 rows in set (0.00 sec)

mysql> select post,count(id) from emp group by post;
+----------------------------+-----------+
| post                       | count(id) |
+----------------------------+-----------+
| operation                  |         5 |
| sale                       |         5 |
| teacher                    |         7 |
| 老男孩驻沙河办事处外交大使 |         1 |
+----------------------------+-----------+
4 rows in set (0.00 sec)

mysql> select post,max(salary) from emp 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,avg(salary) from emp 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)

mysql> select post,sum(salary) from emp 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 emp 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)

mysql> select post,sum(salary) from emp 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,count(id) from emp group by post;
+----------------------------+-----------+
| post                       | count(id) |
+----------------------------+-----------+
| operation                  |         5 |
| sale                       |         5 |
| teacher                    |         7 |
| 老男孩驻沙河办事处外交大使 |         1 |
+----------------------------+-----------+
4 rows in set (0.00 sec)

mysql> select post,count(sex) from emp group by post;
+----------------------------+------------+
| post                       | count(sex) |
+----------------------------+------------+
| operation                  |          5 |
| sale                       |          5 |
| teacher                    |          7 |
| 老男孩驻沙河办事处外交大使 |          1 |
+----------------------------+------------+
4 rows in set (0.00 sec)

 为什么用id呢?
 innodb表达id字段，primary本身就是一个索引用他排序速度很快
统计出每个部门年龄30以上的员工的平均薪资


mysql> select*from emp where max(salary)>3000;
ERROR 1111 (HY000): Invalid use of group function
mysql> select max(salary) from emp;
+-------------+
| max(salary) |
+-------------+
|  1000000.31 |
+-------------+
1 row in set (0.00 sec)

mysql> select*from emp where max(salary)>3000;
ERROR 1111 (HY000): Invalid use of group function
mysql> select max(salary) from emp;
+-------------+
| max(salary) |
+-------------+
|  1000000.31 |
+-------------+
1 row in set (0.00 sec)

concat字符拼接
mysql> select post from emp group by post;
+----------------------------+
| post                       |
+----------------------------+
| operation                  |
| sale                       |
| teacher                    |
| 老男孩驻沙河办事处外交大使 |
+----------------------------+
4 rows in set (0.00 sec)

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,张野
     |
| sale                       | 格格,星星,丁丁,丫丫,歪歪
     |
| teacher                    | 成龙,jinxin,jingliyang,liwenzhou,yuanhao,wupeiqi,
alex |
| 老男孩驻沙河办事处外交大使 | egon
     |
+----------------------------+--------------------------------------------------
-----+
4 rows in set (0.00 sec)

mysql> select post,group_concat_ws(":",name,age,sex) from emp group by post;
ERROR 1305 (42000): FUNCTION sb5.group_concat_ws does not exist
mysql> select post,group_concat(name,age) from emp group by post;
+----------------------------+--------------------------------------------------
-------------------+
| post                       | group_concat(name,age)
                   |
+----------------------------+--------------------------------------------------
-------------------+
| operation                  | 程咬铁18,程咬铜18,程咬银18,程咬金18,张野28
                   |
| sale                       | 格格28,星星18,丁丁18,丫丫38,歪歪48
                   |
| teacher                    | 成龙48,jinxin18,jingliyang18,liwenzhou28,yuanhao7
3,wupeiqi81,alex78 |
| 老男孩驻沙河办事处外交大使 | egon18
                   |
+----------------------------+--------------------------------------------------
-------------------+
4 rows in set (0.00 sec)

mysql> select post,group_concat(name,';',age) from emp group by post;
+----------------------------+--------------------------------------------------
--------------------------+
| post                       | group_concat(name,';',age)
                          |
+----------------------------+--------------------------------------------------
--------------------------+
| operation                  | 程咬铁;18,程咬铜;18,程咬银;18,程咬金;18,张野;28
                          |
| sale                       | 格格;28,星星;18,丁丁;18,丫丫;38,歪歪;48
                          |
| teacher                    | 成龙;48,jinxin;18,jingliyang;18,liwenzhou;28,yuan
hao;73,wupeiqi;81,alex;78 |
| 老男孩驻沙河办事处外交大使 | egon;18
                          |
+----------------------------+--------------------------------------------------
--------------------------+
4 rows in set (0.00 sec)

#4、having 过滤条件
# where是在分组之前的过滤，即在分组之前做了一次整体性的筛选
# having是在分组之后的过滤，即在分组之后专门针对聚合的结果进行进一步的筛选

select post,avg(salary) from emp group by post having avg(salary) > 10000;
select post,avg(salary) from emp group by post ;

mysql> select post,avg(salary) from emp group by post having avg(salary)>10000;
+-----------+---------------+
| post      | avg(salary)   |
+-----------+---------------+
| operation |  16800.026000 |
| teacher   | 151842.901429 |
+-----------+---------------+
2 rows in set (0.00 sec)

mysql> select post,avg(salary) from emp 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)

小练习:

相关小练习:
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
3. 查询各岗位平均薪资大于10000的岗位名、平均工资
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

6、limit 限制显示的条件
select * from emp limit 3;

#薪资最高那个人的详细信息
select * from emp order by salary desc limit 1;

分页显示
select * from emp limit 0,5; # 从0开始往后取5条
select * from emp limit 5,5; #从5开始往后取5条

egon上机笔记

mysql> select*from emp;
+----+------------+--------+-----+------------+----------------------------+--------------+------------+
| id | name       | sex    | age | hire_date  | post                       | post_comment | salary     |
+----+------------+--------+-----+------------+----------------------------+--------------+------------+
|  1 | egon       | male   |  18 | 2017-03-01 | 老男孩驻沙河办事处外交大使 | NULL         |    7300.33 |
|  2 | alex       | male   |  78 | 2015-03-02 | teacher                    | NULL         | 1000000.31 |
|  3 | wupeiqi    | male   |  81 | 2013-03-05 | teacher                    | NULL         |    8300.00 |
|  4 | yuanhao    | male   |  73 | 2014-07-01 | teacher                    | NULL         |    3500.00 |
|  5 | liwenzhou  | male   |  28 | 2012-11-01 | teacher                    | NULL         |    2100.00 |
|  6 | jingliyang | female |  18 | 2011-02-11 | teacher                    | NULL         |    9000.00 |
|  7 | jinxin     | male   |  18 | 1900-03-01 | teacher                    | NULL         |   30000.00 |
|  8 | 成龙       | male   |  48 | 2010-11-11 | teacher                    | NULL         |   10000.00 |
|  9 | 歪歪       | female |  48 | 2015-03-11 | sale                       | NULL         |    3000.13 |
| 10 | 丫丫       | female |  38 | 2010-11-01 | sale                       | NULL         |    2000.35 |
| 11 | 丁丁       | female |  18 | 2011-03-12 | sale                       | NULL         |    1000.37 |
| 12 | 星星       | female |  18 | 2016-05-13 | sale                       | NULL         |    3000.29 |
| 13 | 格格       | female |  28 | 2017-01-27 | sale                       | NULL         |    4000.33 |
| 14 | 张野       | male   |  28 | 2016-03-11 | operation                  | NULL         |   10000.13 |
| 15 | 程咬金     | male   |  18 | 1997-03-12 | operation                  | NULL         |   20000.00 |
| 16 | 程咬银     | female |  18 | 2013-03-11 | operation                  | NULL         |   19000.00 |
| 17 | 程咬铜     | male   |  18 | 2015-04-11 | operation                  | NULL         |   18000.00 |
| 18 | 程咬铁     | female |  18 | 2014-05-12 | operation                  | NULL         |   17000.00 |
+----+------------+--------+-----+------------+----------------------------+--------------+------------+
18 rows in set (0.00 sec)

mysql> select*from emp limit 0,5;
+----+-----------+------+-----+------------+----------------------------+--------------+------------+
| id | name      | sex  | age | hire_date  | post                       | post_comment | salary     |
+----+-----------+------+-----+------------+----------------------------+--------------+------------+
|  1 | egon      | male |  18 | 2017-03-01 | 老男孩驻沙河办事处外交大使 | NULL         |    7300.33 |
|  2 | alex      | male |  78 | 2015-03-02 | teacher                    | NULL         | 1000000.31 |
|  3 | wupeiqi   | male |  81 | 2013-03-05 | teacher                    | NULL         |    8300.00 |
|  4 | yuanhao   | male |  73 | 2014-07-01 | teacher                    | NULL         |    3500.00 |
|  5 | liwenzhou | male |  28 | 2012-11-01 | teacher                    | NULL         |    2100.00 |
+----+-----------+------+-----+------------+----------------------------+--------------+------------+
5 rows in set (0.00 sec)

mysql> select*from emp limit 5,10;
+----+------------+--------+-----+------------+-----------+--------------+----------+
| id | name       | sex    | age | hire_date  | post      | post_comment | salary   |
+----+------------+--------+-----+------------+-----------+--------------+----------+
|  6 | jingliyang | female |  18 | 2011-02-11 | teacher   | NULL         |  9000.00 |
|  7 | jinxin     | male   |  18 | 1900-03-01 | teacher   | NULL         | 30000.00 |
|  8 | 成龙       | male   |  48 | 2010-11-11 | teacher   | NULL         | 10000.00 |
|  9 | 歪歪       | female |  48 | 2015-03-11 | sale      | NULL         |  3000.13 |
| 10 | 丫丫       | female |  38 | 2010-11-01 | sale      | NULL         |  2000.35 |
| 11 | 丁丁       | female |  18 | 2011-03-12 | sale      | NULL         |  1000.37 |
| 12 | 星星       | female |  18 | 2016-05-13 | sale      | NULL         |  3000.29 |
| 13 | 格格       | female |  28 | 2017-01-27 | sale      | NULL         |  4000.33 |
| 14 | 张野       | male   |  28 | 2016-03-11 | operation | NULL         | 10000.13 |
| 15 | 程咬金     | male   |  18 | 1997-03-12 | operation | NULL         | 20000.00 |
+----+------------+--------+-----+------------+-----------+--------------+----------+
10 rows in set (0.00 sec)

mysql> select*from emp limit 10,5;
+----+--------+--------+-----+------------+-----------+--------------+----------+
| id | name   | sex    | age | hire_date  | post      | post_comment | salary   |
+----+--------+--------+-----+------------+-----------+--------------+----------+
| 11 | 丁丁   | female |  18 | 2011-03-12 | sale      | NULL         |  1000.37 |
| 12 | 星星   | female |  18 | 2016-05-13 | sale      | NULL         |  3000.29 |
| 13 | 格格   | female |  28 | 2017-01-27 | sale      | NULL         |  4000.33 |
| 14 | 张野   | male   |  28 | 2016-03-11 | operation | NULL         | 10000.13 |
| 15 | 程咬金 | male   |  18 | 1997-03-12 | operation | NULL         | 20000.00 |
+----+--------+--------+-----+------------+-----------+--------------+----------+
5 rows in set (0.00 sec)

mysql> select*from emp limit 15,5;
+----+--------+--------+-----+------------+-----------+--------------+----------+
| id | name   | sex    | age | hire_date  | post      | post_comment | salary   |
+----+--------+--------+-----+------------+-----------+--------------+----------+
| 16 | 程咬银 | female |  18 | 2013-03-11 | operation | NULL         | 19000.00 |
| 17 | 程咬铜 | male   |  18 | 2015-04-11 | operation | NULL         | 18000.00 |
| 18 | 程咬铁 | female |  18 | 2014-05-12 | operation | NULL         | 17000.00 |
+----+--------+--------+-----+------------+-----------+--------------+----------+
3 rows in set (0.00 sec)

#正则表达式
select * from emp where name regexp "^jin.*(g|n)$";
#1、笛卡儿积

select * from emp,dep; #左表和右表全部建立对应关系

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

select * from emp,dep where emp.dep_id = dep.id and dep.name = "技术";

#2、内连接：只取两张表有对应关系的记录 #where专门干筛选的活
select * from emp inner join dep on emp.dep_id = dep.id;
select * from emp inner join dep on emp.dep_id = dep.id
where dep.name = "技术";


#3、左连接: 在内连接的基础上保留左表没有对应关系的记录
select * from emp left join dep on emp.dep_id = dep.id;

#4、右连接: 在内连接的基础上保留右表没有对应关系的记录
select * from emp right join dep on emp.dep_id = dep.id;

#5、全连接：在内连接的基础上保留左、右面表没有对应关系的的记录
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;

egon上机笔记

mysql> create database sb5 charset gbk;
Query OK, 1 row affected (0.00 sec)

mysql> use sb5;
Database changed
mysql> create table department(
    -> id int,
    -> name varchar(20)
    -> );
Query OK, 0 rows affected (0.01 sec)

mysql>
mysql> create table employee(
    -> id int primary key auto_increment,
    -> name varchar(20),
    -> sex enum('male','female') not null default 'male',
    -> age int,
    -> dep_id int
    -> );
Query OK, 0 rows affected (0.01 sec)

mysql> desc department;
+-------+-------------+------+-----+---------+-------+
| Field | Type        | Null | Key | Default | Extra |
+-------+-------------+------+-----+---------+-------+
| id    | int(11)     | YES  |     | NULL    |       |
| name  | varchar(20) | YES  |     | NULL    |       |
+-------+-------------+------+-----+---------+-------+
2 rows in set (0.01 sec)

mysql> desc employee;
+--------+-----------------------+------+-----+---------+----------------+
| Field  | Type                  | Null | Key | Default | Extra          |
+--------+-----------------------+------+-----+---------+----------------+
| id     | int(11)               | NO   | PRI | NULL    | auto_increment |
| name   | varchar(20)           | YES  |     | NULL    |                |
| sex    | enum('male','female') | NO   |     | male    |                |
| age    | int(11)               | YES  |     | NULL    |                |
| dep_id | int(11)               | YES  |     | NULL    |                |
+--------+-----------------------+------+-----+---------+----------------+
5 rows in set (0.01 sec)

mysql> insert into department values
    -> (200,'技术'),
    -> (201,'人力资源'),
    -> (202,'销售'),
    -> (203,'运营');
Query OK, 4 rows affected (0.00 sec)
Records: 4  Duplicates: 0  Warnings: 0

mysql> insert into employee(name,sex,age,dep_id) values
    -> ('egon','male',18,200),
    -> ('alex','female',48,201),
    -> ('wupeiqi','male',38,201),
    -> ('yuanhao','female',28,202),
    -> ('liwenzhou','male',18,200),
    -> ('jingliyang','female',18,204)
    -> ;
Query OK, 6 rows affected (0.00 sec)
Records: 6  Duplicates: 0  Warnings: 0

mysql> alter table department rename dep;
Query OK, 0 rows affected (0.01 sec)

mysql> select*from employee;
+----+------------+--------+------+--------+
| id | name       | sex    | age  | dep_id |
+----+------------+--------+------+--------+
|  1 | egon       | male   |   18 |    200 |
|  2 | alex       | female |   48 |    201 |
|  3 | wupeiqi    | male   |   38 |    201 |
|  4 | yuanhao    | female |   28 |    202 |
|  5 | liwenzhou  | male   |   18 |    200 |
|  6 | jingliyang | female |   18 |    204 |
+----+------------+--------+------+--------+
6 rows in set (0.00 sec)

mysql> alter table employee rename empp;
Query OK, 0 rows affected (0.01 sec)

mysql> select*from dep;
+------+----------+
| id   | name     |
+------+----------+
|  200 | 技术     |
|  201 | 人力资源 |
|  202 | 销售     |
|  203 | 运营     |
+------+----------+
4 rows in set (0.00 sec)

mysql> select*from empp,dep;
+----+------------+--------+------+--------+------+----------+
| id | name       | sex    | age  | dep_id | id   | name     |
+----+------------+--------+------+--------+------+----------+
|  1 | egon       | male   |   18 |    200 |  200 | 技术     |
|  1 | egon       | male   |   18 |    200 |  201 | 人力资源 |
|  1 | egon       | male   |   18 |    200 |  202 | 销售     |
|  1 | egon       | male   |   18 |    200 |  203 | 运营     |
|  2 | alex       | female |   48 |    201 |  200 | 技术     |
|  2 | alex       | female |   48 |    201 |  201 | 人力资源 |
|  2 | alex       | female |   48 |    201 |  202 | 销售     |
|  2 | alex       | female |   48 |    201 |  203 | 运营     |
|  3 | wupeiqi    | male   |   38 |    201 |  200 | 技术     |
|  3 | wupeiqi    | male   |   38 |    201 |  201 | 人力资源 |
|  3 | wupeiqi    | male   |   38 |    201 |  202 | 销售     |
|  3 | wupeiqi    | male   |   38 |    201 |  203 | 运营     |
|  4 | yuanhao    | female |   28 |    202 |  200 | 技术     |
|  4 | yuanhao    | female |   28 |    202 |  201 | 人力资源 |
|  4 | yuanhao    | female |   28 |    202 |  202 | 销售     |
|  4 | yuanhao    | female |   28 |    202 |  203 | 运营     |
|  5 | liwenzhou  | male   |   18 |    200 |  200 | 技术     |
|  5 | liwenzhou  | male   |   18 |    200 |  201 | 人力资源 |
|  5 | liwenzhou  | male   |   18 |    200 |  202 | 销售     |
|  5 | liwenzhou  | male   |   18 |    200 |  203 | 运营     |
|  6 | jingliyang | female |   18 |    204 |  200 | 技术     |
|  6 | jingliyang | female |   18 |    204 |  201 | 人力资源 |
|  6 | jingliyang | female |   18 |    204 |  202 | 销售     |
|  6 | jingliyang | female |   18 |    204 |  203 | 运营     |
+----+------------+--------+------+--------+------+----------+
24 rows in set (0.01 sec)

连成一张大的表然后单表去查就可以了

mysql> select*from empp,dep where empp.dep_id = dep.id;
+----+-----------+--------+------+--------+------+----------+
| id | name      | sex    | age  | dep_id | id   | name     |
+----+-----------+--------+------+--------+------+----------+
|  1 | egon      | male   |   18 |    200 |  200 | 技术     |
|  2 | alex      | female |   48 |    201 |  201 | 人力资源 |
|  3 | wupeiqi   | male   |   38 |    201 |  201 | 人力资源 |
|  4 | yuanhao   | female |   28 |    202 |  202 | 销售     |
|  5 | liwenzhou | male   |   18 |    200 |  200 | 技术     |
+----+-----------+--------+------+--------+------+----------+
5 rows in set (0.00 sec)

mysql> select*from empp,dep where empp.dep_id=dep.id and dep.name="技术";
+----+-----------+------+------+--------+------+------+
| id | name      | sex  | age  | dep_id | id   | name |
+----+-----------+------+------+--------+------+------+
|  1 | egon      | male |   18 |    200 |  200 | 技术 |
|  5 | liwenzhou | male |   18 |    200 |  200 | 技术 |
+----+-----------+------+------+--------+------+------+
2 rows in set (0.00 sec)

mysql> select * from empp inner join dep on empp.dep_id = dep.id
    ->                             where dep.name = "技术";
+----+-----------+------+------+--------+------+------+
| id | name      | sex  | age  | dep_id | id   | name |
+----+-----------+------+------+--------+------+------+
|  1 | egon      | male |   18 |    200 |  200 | 技术 |
|  5 | liwenzhou | male |   18 |    200 |  200 | 技术 |
+----+-----------+------+------+--------+------+------+
2 rows in set (0.00 sec)

mysql> select * from empp left join dep on empp.dep_id = dep.id;
+----+------------+--------+------+--------+------+----------+
| id | name       | sex    | age  | dep_id | id   | name     |
+----+------------+--------+------+--------+------+----------+
|  1 | egon       | male   |   18 |    200 |  200 | 技术     |
|  5 | liwenzhou  | male   |   18 |    200 |  200 | 技术     |
|  2 | alex       | female |   48 |    201 |  201 | 人力资源 |
|  3 | wupeiqi    | male   |   38 |    201 |  201 | 人力资源 |
|  4 | yuanhao    | female |   28 |    202 |  202 | 销售     |
|  6 | jingliyang | female |   18 |    204 | NULL | NULL     |
+----+------------+--------+------+--------+------+----------+
6 rows in set (0.00 sec)

mysql> select * from empp right join dep on empp.dep_id = dep.id;
+------+-----------+--------+------+--------+------+----------+
| id   | name      | sex    | age  | dep_id | id   | name     |
+------+-----------+--------+------+--------+------+----------+
|    1 | egon      | male   |   18 |    200 |  200 | 技术     |
|    2 | alex      | female |   48 |    201 |  201 | 人力资源 |
|    3 | wupeiqi   | male   |   38 |    201 |  201 | 人力资源 |
|    4 | yuanhao   | female |   28 |    202 |  202 | 销售     |
|    5 | liwenzhou | male   |   18 |    200 |  200 | 技术     |
| NULL | NULL      | NULL   | NULL |   NULL |  203 | 运营     |
+------+-----------+--------+------+--------+------+----------+
6 rows in set (0.00 sec)

mysql> select * from empp left join dep on empp.dep_id = dep.id
    -> union
    -> select * from empp right join dep on empp.dep_id = dep.id;
+------+------------+--------+------+--------+------+----------+
| id   | name       | sex    | age  | dep_id | id   | name     |
+------+------------+--------+------+--------+------+----------+
|    1 | egon       | male   |   18 |    200 |  200 | 技术     |
|    5 | liwenzhou  | male   |   18 |    200 |  200 | 技术     |
|    2 | alex       | female |   48 |    201 |  201 | 人力资源 |
|    3 | wupeiqi    | male   |   38 |    201 |  201 | 人力资源 |
|    4 | yuanhao    | female |   28 |    202 |  202 | 销售     |
|    6 | jingliyang | female |   18 |    204 | NULL | NULL     |
| NULL | NULL       | NULL   | NULL |   NULL |  203 | 运营     |
+------+------------+--------+------+--------+------+----------+
7 rows in set (0.01 sec)