SQL自学，mysql从入门到精通 --- 第 15天，数据导入、导出

news2025/2/12 18:45:41

数据的导入、导出

-- 查看当前设置的目录路径，限制从数据库服务器读取和写入文件的操作只能在指定的目录中进行,在安全性和文件操作限制方面具有重要意义。

root@mysqldb 14:19:  [(none)]> SHOW VARIABLES LIKE "secure_file_priv";
+------------------+-------------------+
| Variable_name    | Value             |
+------------------+-------------------+
| secure_file_priv | /data/mysql/data/ |
+------------------+-------------------+
1 row in set (0.02 sec)


#配置文件
[root@mrloam ~]# grep secure_file_priv /etc/my.cnf 
secure_file_priv = /data/mysql/data

1.数据导入

root@mysqldb 14:40:  [(none)]> CREATE TABLE db3.user (
    -> name VARCHAR(30),
    -> password VARCHAR(8),
    -> uid INT,
    -> gid INT,
    -> comment VARCHAR(150),
    -> homedir CHAR(80),
    -> shell CHAR(60)
    -> );
Query OK, 0 rows affected (0.01 sec)

root@mysqldb 14:40:  [(none)]> DESC db3.user;
+----------+--------------+------+-----+---------+-------+
| Field    | Type         | Null | Key | Default | Extra |
+----------+--------------+------+-----+---------+-------+
| name     | varchar(30)  | YES  |     | NULL    |       |
| password | varchar(8)   | YES  |     | NULL    |       |
| uid      | int(11)      | YES  |     | NULL    |       |
| gid      | int(11)      | YES  |     | NULL    |       |
| comment  | varchar(150) | YES  |     | NULL    |       |
| homedir  | char(80)     | YES  |     | NULL    |       |
| shell    | char(60)     | YES  |     | NULL    |       |
+----------+--------------+------+-----+---------+-------+
7 rows in set (0.01 sec)

root@mysqldb 14:40:  [(none)]> SELECT * FROM db3.user;
Empty set (0.00 sec)



-- 准备数据文件
root@mysqldb 14:41:  [(none)]> system cp /etc/passwd /data/mysql/data/
root@mysqldb 14:42:  [(none)]> system ls /data/mysql/data/
auto.cnf	 client-key.pem  ibdata1      mysql		  public_key.pem	    sys
ca-key.pem	 d1		 ib_logfile0  passwd		  server-cert.pem
ca.pem		 db3		 ib_logfile1  performance_schema  server-key.pem
client-cert.pem  ib_buffer_pool  ibtmp1       private_key.pem	  sql_self_learning_skills

-- 导入数据
root@mysqldb 14:43:  [(none)]> load data infile "/data/mysql/data/passwd" into table db3.user fields terminated by ":" lines terminated by "\n";
Query OK, 21 rows affected (0.00 sec)
Records: 21  Deleted: 0  Skipped: 0  Warnings: 0

root@mysqldb 14:45:  [(none)]> alter table db3.user  add  id  int  primary key  auto_increment first;
Query OK, 0 rows affected (0.16 sec)
Records: 0  Duplicates: 0  Warnings: 0

root@mysqldb 14:46:  [(none)]> select  * from db3.user ;
+----+-----------------+----------+------+------+----------------------------+--------------------+----------------+
| id | name            | password | uid  | gid  | comment                    | homedir            | shell          |
+----+-----------------+----------+------+------+----------------------------+--------------------+----------------+
|  1 | root            | x        |    0 |    0 | root                       | /root              | /bin/bash      |
|  2 | bin             | x        |    1 |    1 | bin                        | /bin               | /sbin/nologin  |
|  3 | daemon          | x        |    2 |    2 | daemon                     | /sbin              | /sbin/nologin  |
|  4 | adm             | x        |    3 |    4 | adm                        | /var/adm           | /sbin/nologin  |
|  5 | lp              | x        |    4 |    7 | lp                         | /var/spool/lpd     | /sbin/nologin  |
|  6 | sync            | x        |    5 |    0 | sync                       | /sbin              | /bin/sync      |
|  7 | shutdown        | x        |    6 |    0 | shutdown                   | /sbin              | /sbin/shutdown |
|  8 | halt            | x        |    7 |    0 | halt                       | /sbin              | /sbin/halt     |
|  9 | mail            | x        |    8 |   12 | mail                       | /var/spool/mail    | /sbin/nologin  |
| 10 | operator        | x        |   11 |    0 | operator                   | /root              | /sbin/nologin  |
| 11 | games           | x        |   12 |  100 | games                      | /usr/games         | /sbin/nologin  |
| 12 | ftp             | x        |   14 |   50 | FTP User                   | /var/ftp           | /sbin/nologin  |
| 13 | nobody          | x        |   99 |   99 | Nobody                     | /                  | /sbin/nologin  |
| 14 | systemd-network | x        |  192 |  192 | systemd Network Management | /                  | /sbin/nologin  |
| 15 | dbus            | x        |   81 |   81 | System message bus         | /                  | /sbin/nologin  |
| 16 | polkitd         | x        |  999 |  998 | User for polkitd           | /                  | /sbin/nologin  |
| 17 | sshd            | x        |   74 |   74 | Privilege-separated SSH    | /var/empty/sshd    | /sbin/nologin  |
| 18 | postfix         | x        |   89 |   89 |                            | /var/spool/postfix | /sbin/nologin  |
| 19 | chrony          | x        |  998 |  996 |                            | /var/lib/chrony    | /sbin/nologin  |
| 20 | mysql           | x        | 1000 | 1000 |                            | /home/mysql        | /sbin/nologin  |
| 21 | test            | x        | 1001 | 1001 |                            | /home/test         | /bin/bash      |
+----+-----------------+----------+------+------+----------------------------+--------------------+----------------+
21 rows in set (0.00 sec)

2.数据导出

把表记录存储到系统文件里

批量处理数据

命令格式:

sql查询命令 into outfile “目录/文件名”

[ fields terminated by “列间隔符号” lines terminated by “行间隔符号”];

-- 数据导出
root@mysqldb 14:47:  [(none)]> select * from db3.user where id <= 10 into outfile "/data/mysql/data/a.txt";
Query OK, 10 rows affected (0.00 sec)

root@mysqldb 14:51:  [(none)]> select  name ,shell from db3.user  into outfile "/data/mysql/data/b.txt" fields terminated  by "###";
Query OK, 21 rows affected (0.00 sec)

root@mysqldb 14:51:  [(none)]> select name , shell ,  uid  from  db3.user where id <= 3
    -> into outfile  "/data/mysql/data/c.txt"
    -> fields terminated by "????" lines terminated by "###" ;
Query OK, 3 rows affected (0.00 sec)


#查看
[root@mrloam ~]# cat /data/mysql/data/a.txt 
1	root	x	0	0	root	/root	/bin/bash
2	bin	x	1	1	bin	/bin	/sbin/nologin
3	daemon	x	2	2	daemon	/sbin	/sbin/nologin
4	adm	x	3	4	adm	/var/adm	/sbin/nologin
5	lp	x	4	7	lp	/var/spool/lpd	/sbin/nologin
6	sync	x	5	0	sync	/sbin	/bin/sync
7	shutdown	x	6	0	shutdown	/sbin	/sbin/shutdown
8	halt	x	7	0	halt	/sbin	/sbin/halt
9	mail	x	8	12	mail	/var/spool/mail	/sbin/nologin
10	operator	x	11	0	operator	/root	/sbin/nologin

[root@mrloam ~]# cat /data/mysql/data/b.txt 
root###/bin/bash
bin###/sbin/nologin
daemon###/sbin/nologin
adm###/sbin/nologin
lp###/sbin/nologin
sync###/bin/sync
shutdown###/sbin/shutdown
halt###/sbin/halt
mail###/sbin/nologin
operator###/sbin/nologin
games###/sbin/nologin
ftp###/sbin/nologin
nobody###/sbin/nologin
systemd-network###/sbin/nologin
dbus###/sbin/nologin
polkitd###/sbin/nologin
sshd###/sbin/nologin
postfix###/sbin/nologin
chrony###/sbin/nologin
mysql###/sbin/nologin
test###/bin/bash

[root@mrloam ~]# cat /data/mysql/data/c.txt 
root????/bin/bash????0###bin????/sbin/nologin????1###daemon????/sbin/nologin????2###

3.管理表记录

root@mysqldb 15:06:  [(none)]> insert  into  db3.user
    -> values
    -> (22,"tom","x",2001,2001,"test user","/home/tom","/bin/bash"), 
    -> (23,"tom","x",2001,2001,"test user","/home/tom","/bin/bash"), 
    -> (24,"tom","x",2001,2001,"test user","/home/tom","/bin/bash");
Query OK, 3 rows affected (0.00 sec)
Records: 3  Duplicates: 0  Warnings: 0



root@mysqldb 14:59:  [(none)]> insert into  db3.user(name,uid,shell) values("bob",3000,"/bin/bash");
Query OK, 1 row affected (0.00 sec)

root@mysqldb 15:00:  [(none)]> insert into  db3.user(name,uid,shell) 
    ->   values
    ->   ("bobf",3000,"/bin/bash"),("bobc",3003,"/bin/bash"),("bobA",3002,"/bin/bash");
Query OK, 3 rows affected (0.00 sec)
Records: 3  Duplicates: 0  Warnings: 0



root@mysqldb 15:01:  [(none)]> select  *  from  db3.user where  shell = "/sbin/nologin" ;
+----+-----------------+----------+------+------+----------------------------+--------------------+-------------
| id | name            | password | uid  | gid  | comment                    | homedir            | shell       
+----+-----------------+----------+------+------+----------------------------+--------------------+-------------
|  2 | bin             | x        |    1 |    1 | bin                        | /bin               | /sbin/nologi
|  3 | daemon          | x        |    2 |    2 | daemon                     | /sbin              | /sbin/nologi
|  4 | adm             | x        |    3 |    4 | adm                        | /var/adm           | /sbin/nologi
|  5 | lp              | x        |    4 |    7 | lp                         | /var/spool/lpd     | /sbin/nologi
|  9 | mail            | x        |    8 |   12 | mail                       | /var/spool/mail    | /sbin/nologi
| 10 | operator        | x        |   11 |    0 | operator                   | /root              | /sbin/nologi
| 11 | games           | x        |   12 |  100 | games                      | /usr/games         | /sbin/nologi
| 12 | ftp             | x        |   14 |   50 | FTP User                   | /var/ftp           | /sbin/nologi
| 13 | nobody          | x        |   99 |   99 | Nobody                     | /                  | /sbin/nologi
| 14 | systemd-network | x        |  192 |  192 | systemd Network Management | /                  | /sbin/nologi
| 15 | dbus            | x        |   81 |   81 | System message bus         | /                  | /sbin/nologi
| 16 | polkitd         | x        |  999 |  998 | User for polkitd           | /                  | /sbin/nologi
| 17 | sshd            | x        |   74 |   74 | Privilege-separated SSH    | /var/empty/sshd    | /sbin/nologi
| 18 | postfix         | x        |   89 |   89 |                            | /var/spool/postfix | /sbin/nologi
| 19 | chrony          | x        |  998 |  996 |                            | /var/lib/chrony    | /sbin/nologi
| 20 | mysql           | x        | 1000 | 1000 |                            | /home/mysql        | /sbin/nologi
+----+-----------------+----------+------+------+----------------------------+--------------------+-------------
16 rows in set (0.00 sec)

root@mysqldb 15:01:  [(none)]> select  name , shell  from  db3.user where  shell = "/sbin/nologin" ;
+-----------------+---------------+
| name            | shell         |
+-----------------+---------------+
| bin             | /sbin/nologin |
| daemon          | /sbin/nologin |
| adm             | /sbin/nologin |
| lp              | /sbin/nologin |
| mail            | /sbin/nologin |
| operator        | /sbin/nologin |
| games           | /sbin/nologin |
| ftp             | /sbin/nologin |
| nobody          | /sbin/nologin |
| systemd-network | /sbin/nologin |
| dbus            | /sbin/nologin |
| polkitd         | /sbin/nologin |
| sshd            | /sbin/nologin |
| postfix         | /sbin/nologin |
| chrony          | /sbin/nologin |
| mysql           | /sbin/nologin |
+-----------------+---------------+
16 rows in set (0.00 sec)


root@mysqldb 15:01:  [(none)]> update  db3.user set password="A" , comment="student" ;
Query OK, 28 rows affected (0.00 sec)
Rows matched: 28  Changed: 28  Warnings: 0

root@mysqldb 15:02:  [(none)]> update db3.user set  password="x" , comment="root" where name="root";
Query OK, 1 row affected (0.00 sec)
Rows matched: 1  Changed: 1  Warnings: 0


root@mysqldb 15:02:  [(none)]> delete from  db3.user where  id >= 21 ;
Query OK, 8 rows affected (0.00 sec)


root@mysqldb 15:07:  [(none)]> select  name  ,  uid  , gid   from db3.user  where  uid  !=  gid ;
+----------+------+------+
| name     | uid  | gid  |
+----------+------+------+
| adm      |    3 |    4 |
| lp       |    4 |    7 |
| sync     |    5 |    0 |
| shutdown |    6 |    0 |
| halt     |    7 |    0 |
| mail     |    8 |   12 |
| operator |   11 |    0 |
| games    |   12 |  100 |
| ftp      |   14 |   50 |
| polkitd  |  999 |  998 |
| chrony   |  998 |  996 |
+----------+------+------+
11 rows in set (0.00 sec)

root@mysqldb 15:08:  [(none)]> select  name  ,  uid  , gid   from db3.user  where  uid  !=  gid ;
+----------+------+------+
| name     | uid  | gid  |
+----------+------+------+
| adm      |    3 |    4 |
| lp       |    4 |    7 |
| sync     |    5 |    0 |
| shutdown |    6 |    0 |
| halt     |    7 |    0 |
| mail     |    8 |   12 |
| operator |   11 |    0 |
| games    |   12 |  100 |
| ftp      |   14 |   50 |
| polkitd  |  999 |  998 |
| chrony   |  998 |  996 |
+----------+------+------+
11 rows in set (0.00 sec)

root@mysqldb 15:08:  [(none)]> select  *   from db3.user  where  id <= 5 ;
+----+--------+----------+------+------+---------+----------------+---------------+
| id | name   | password | uid  | gid  | comment | homedir        | shell         |
+----+--------+----------+------+------+---------+----------------+---------------+
|  1 | root   | x        |    0 |    0 | root    | /root          | /bin/bash     |
|  2 | bin    | A        |    1 |    1 | student | /bin           | /sbin/nologin |
|  3 | daemon | A        |    2 |    2 | student | /sbin          | /sbin/nologin |
|  4 | adm    | A        |    3 |    4 | student | /var/adm       | /sbin/nologin |
|  5 | lp     | A        |    4 |    7 | student | /var/spool/lpd | /sbin/nologin |
+----+--------+----------+------+------+---------+----------------+---------------+
5 rows in set (0.00 sec)

root@mysqldb 15:09:  [(none)]> select name  , shell  from  db3.user where  shell != "/bin/bash" ;
+-----------------+----------------+
| name            | shell          |
+-----------------+----------------+
| bin             | /sbin/nologin  |
| daemon          | /sbin/nologin  |
| adm             | /sbin/nologin  |
| lp              | /sbin/nologin  |
| sync            | /bin/sync      |
| shutdown        | /sbin/shutdown |
| halt            | /sbin/halt     |
| mail            | /sbin/nologin  |
| operator        | /sbin/nologin  |
| games           | /sbin/nologin  |
| ftp             | /sbin/nologin  |
| nobody          | /sbin/nologin  |
| systemd-network | /sbin/nologin  |
| dbus            | /sbin/nologin  |
| polkitd         | /sbin/nologin  |
| sshd            | /sbin/nologin  |
| postfix         | /sbin/nologin  |
| chrony          | /sbin/nologin  |
| mysql           | /sbin/nologin  |
+-----------------+----------------+
19 rows in set (0.00 sec)

root@mysqldb 15:09:  [(none)]> select  name  , uid  , shell from  db3.user where  shell is not  null ;
+-----------------+------+----------------+
| name            | uid  | shell          |
+-----------------+------+----------------+
| root            |    0 | /bin/bash      |
| bin             |    1 | /sbin/nologin  |
| daemon          |    2 | /sbin/nologin  |
| adm             |    3 | /sbin/nologin  |
| lp              |    4 | /sbin/nologin  |
| sync            |    5 | /bin/sync      |
| shutdown        |    6 | /sbin/shutdown |
| halt            |    7 | /sbin/halt     |
| mail            |    8 | /sbin/nologin  |
| operator        |   11 | /sbin/nologin  |
| games           |   12 | /sbin/nologin  |
| ftp             |   14 | /sbin/nologin  |
| nobody          |   99 | /sbin/nologin  |
| systemd-network |  192 | /sbin/nologin  |
| dbus            |   81 | /sbin/nologin  |
| polkitd         |  999 | /sbin/nologin  |
| sshd            |   74 | /sbin/nologin  |
| postfix         |   89 | /sbin/nologin  |
| chrony          |  998 | /sbin/nologin  |
| mysql           | 1000 | /sbin/nologin  |
+-----------------+------+----------------+
20 rows in set (0.00 sec)

root@mysqldb 15:09:  [(none)]> select  name  , uid  , shell from  db3.user where  shell is null ;
Empty set (0.00 sec)




root@mysqldb 15:10:  [(none)]> select name , uid from  db3.user where uid in (3 ,6,9,11);
+----------+------+
| name     | uid  |
+----------+------+
| adm      |    3 |
| shutdown |    6 |
| operator |   11 |
+----------+------+
3 rows in set (0.00 sec)

root@mysqldb 15:10:  [(none)]> select shell  from  db3.user where  shell not  in  ("/bin/bash","/sbin/nologin"); 
+----------------+
| shell          |
+----------------+
| /bin/sync      |
| /sbin/shutdown |
| /sbin/halt     |
+----------------+
3 rows in set (0.00 sec)


root@mysqldb 15:10:  [(none)]> select name , uid  from  db3.user 
    -> where  name = "sync" or  name = "apache" or  uid=3;
+------+------+
| name | uid  |
+------+------+
| adm  |    3 |
| sync |    5 |
+------+------+
2 rows in set (0.00 sec)

root@mysqldb 15:11:  [(none)]> select  * from  db3.user where id >= 10  and  id <= 20 ;
+----+-----------------+----------+------+------+---------+--------------------+---------------+
| id | name            | password | uid  | gid  | comment | homedir            | shell         |
+----+-----------------+----------+------+------+---------+--------------------+---------------+
| 10 | operator        | A        |   11 |    0 | student | /root              | /sbin/nologin |
| 11 | games           | A        |   12 |  100 | student | /usr/games         | /sbin/nologin |
| 12 | ftp             | A        |   14 |   50 | student | /var/ftp           | /sbin/nologin |
| 13 | nobody          | A        |   99 |   99 | student | /                  | /sbin/nologin |
| 14 | systemd-network | A        |  192 |  192 | student | /                  | /sbin/nologin |
| 15 | dbus            | A        |   81 |   81 | student | /                  | /sbin/nologin |
| 16 | polkitd         | A        |  999 |  998 | student | /                  | /sbin/nologin |
| 17 | sshd            | A        |   74 |   74 | student | /var/empty/sshd    | /sbin/nologin |
| 18 | postfix         | A        |   89 |   89 | student | /var/spool/postfix | /sbin/nologin |
| 19 | chrony          | A        |  998 |  996 | student | /var/lib/chrony    | /sbin/nologin |
| 20 | mysql           | A        | 1000 | 1000 | student | /home/mysql        | /sbin/nologin |
+----+-----------------+----------+------+------+---------+--------------------+---------------+
11 rows in set (0.00 sec)

-- || 也可以表示或
root@mysqldb 15:11:  [(none)]> select name , uid  from  db3.user 
    -> where  name = "sync" ||  name = "apache"  ||  uid=3;
+------+------+
| name | uid  |
+------+------+
| adm  |    3 |
| sync |    5 |
+------+------+
2 rows in set (0.00 sec)

-- && 表示and
root@mysqldb 15:11:  [(none)]> select  * from  db3.user where id >= 10 &&  id <= 20 ;
+----+-----------------+----------+------+------+---------+--------------------+---------------+
| id | name            | password | uid  | gid  | comment | homedir            | shell         |
+----+-----------------+----------+------+------+---------+--------------------+---------------+
| 10 | operator        | A        |   11 |    0 | student | /root              | /sbin/nologin |
| 11 | games           | A        |   12 |  100 | student | /usr/games         | /sbin/nologin |
| 12 | ftp             | A        |   14 |   50 | student | /var/ftp           | /sbin/nologin |
| 13 | nobody          | A        |   99 |   99 | student | /                  | /sbin/nologin |
| 14 | systemd-network | A        |  192 |  192 | student | /                  | /sbin/nologin |
| 15 | dbus            | A        |   81 |   81 | student | /                  | /sbin/nologin |
| 16 | polkitd         | A        |  999 |  998 | student | /                  | /sbin/nologin |
| 17 | sshd            | A        |   74 |   74 | student | /var/empty/sshd    | /sbin/nologin |
| 18 | postfix         | A        |   89 |   89 | student | /var/spool/postfix | /sbin/nologin |
| 19 | chrony          | A        |  998 |  996 | student | /var/lib/chrony    | /sbin/nologin |
| 20 | mysql           | A        | 1000 | 1000 | student | /home/mysql        | /sbin/nologin |
+----+-----------------+----------+------+------+---------+--------------------+---------------+
11 rows in set (0.00 sec)


-- 查询的优先级
root@mysqldb 15:15:  [(none)]> select  name , uid  from  db3.user  where   uid = 1 or  uid = 0  and  name = "root" ;
+------+------+
| name | uid  |
+------+------+
| root |    0 |
| bin  |    1 |
+------+------+
2 rows in set (0.00 sec)

root@mysqldb 15:15:  [(none)]> 
root@mysqldb 15:16:  [(none)]> 
root@mysqldb 15:16:  [(none)]> select  name , uid  from  db3.user   where  ( uid = 1 or  uid = 0 )  and  name = "root";
+------+------+
| name | uid  |
+------+------+
| root |    0 |
+------+------+
1 row in set (0.00 sec)

通配符 _ %

root@mysqldb 15:16:  [(none)]> select  name  from  db3.user where  name like  '___';
+------+
| name |
+------+
| bin  |
| adm  |
| ftp  |
+------+
3 rows in set (0.00 sec)

root@mysqldb 15:29:  [(none)]> select  name  from  db3.user where  name like  '____';
+------+
| name |
+------+
| root |
| sync |
| halt |
| mail |
| dbus |
| sshd |
+------+
6 rows in set (0.00 sec)

root@mysqldb 15:29:  [(none)]> select  name  from  db3.user where  name like  '%a%';
+----------+
| name     |
+----------+
| daemon   |
| adm      |
| halt     |
| mail     |
| operator |
| games    |
+----------+
6 rows in set (0.00 sec)

root@mysqldb 15:29:  [(none)]> select  name  from  db3.user where  name like  'a%';
+------+
| name |
+------+
| adm  |
+------+
1 row in set (0.00 sec)

root@mysqldb 15:29:  [(none)]> select  name  from  db3.user where  name like  '___%___';
+-----------------+
| name            |
+-----------------+
| daemon          |
| shutdown        |
| operator        |
| nobody          |
| systemd-network |
| polkitd         |
| postfix         |
| chrony          |
+-----------------+
8 rows in set (0.00 sec)

正则匹配 regexp

where 字段名 regexp ‘正则表达式’
^ $ . * [] |

^：匹配字符串的开头
$：匹配字符串的结尾
.：匹配任意字符（除了换行符）
*：匹配前面的字符零次或多次
[]：匹配方括号中的任意一个字符
|：表示“或”的关系，匹配多个选项中的一个

​

root@mysqldb 15:29:  [(none)]> insert into  db3.user(name) values ("yaya9"),("y7aya"),("ya6ya"),("3yaya");
Query OK, 4 rows affected (0.00 sec)
Records: 4  Duplicates: 0  Warnings: 0

root@mysqldb 15:31:  [(none)]> select  name  from  db3.user where name regexp '[0-9]';
+-------+
| name  |
+-------+
| yaya9 |
| y7aya |
| ya6ya |
| 3yaya |
+-------+
4 rows in set (0.00 sec)

root@mysqldb 15:31:  [(none)]> select  name  from  db3.user where  name regexp  '^[0-9]';
+-------+
| name  |
+-------+
| 3yaya |
+-------+
1 row in set (0.00 sec)

root@mysqldb 15:31:  [(none)]> select name , uid  from   db3.user where  uid  regexp '..' ;
+-----------------+------+
| name            | uid  |
+-----------------+------+
| operator        |   11 |
| games           |   12 |
| ftp             |   14 |
| nobody          |   99 |
| systemd-network |  192 |
| dbus            |   81 |
| polkitd         |  999 |
| sshd            |   74 |
| postfix         |   89 |
| chrony          |  998 |
| mysql           | 1000 |
+-----------------+------+
11 rows in set (0.00 sec)

root@mysqldb 15:31:  [(none)]> select name , uid  from   db3.user where  uid  regexp '^..$' ;
+----------+------+
| name     | uid  |
+----------+------+
| operator |   11 |
| games    |   12 |
| ftp      |   14 |
| nobody   |   99 |
| dbus     |   81 |
| sshd     |   74 |
| postfix  |   89 |
+----------+------+
7 rows in set (0.00 sec)

root@mysqldb 15:31:  [(none)]> select name , uid  from   db3.user where  name  regexp '^a.*t$' ;
Empty set (0.00 sec)

root@mysqldb 15:32:  [(none)]> select name , uid  from   db3.user where  name  regexp '^r|t$' ;
+------+------+
| name | uid  |
+------+------+
| root |    0 |
| halt |    7 |
+------+------+
2 rows in set (0.00 sec)

±*/%

root@mysqldb 15:36:  [(none)]> update db3.user set uid=uid+1   where id <= 5;
Query OK, 5 rows affected (0.00 sec)
Rows matched: 5  Changed: 5  Warnings: 0

root@mysqldb 15:38:  [(none)]> update db3.user set uid=uid-1   where id <= 5;
Query OK, 5 rows affected (0.00 sec)
Rows matched: 5  Changed: 5  Warnings: 0

root@mysqldb 15:38:  [(none)]> alter table db3.user add age tinyint unsigned  not null default 19 after name ;
Query OK, 0 rows affected (0.05 sec)
Records: 0  Duplicates: 0  Warnings: 0

root@mysqldb 15:38:  [(none)]> select name  ,  2020  - age  s_year  from  db3.user where name = "root" ;
+------+--------+
| name | s_year |
+------+--------+
| root |   2001 |
+------+--------+
1 row in set (0.00 sec)

root@mysqldb 15:38:  [(none)]> select name  ,  2020  - age  s_year  from  db3.user ;
+-----------------+--------+
| name            | s_year |
+-----------------+--------+
| root            |   2001 |
| bin             |   2001 |
| daemon          |   2001 |
| adm             |   2001 |
| lp              |   2001 |
| sync            |   2001 |
| shutdown        |   2001 |
| halt            |   2001 |
| mail            |   2001 |
| operator        |   2001 |
| games           |   2001 |
| ftp             |   2001 |
| nobody          |   2001 |
| systemd-network |   2001 |
| dbus            |   2001 |
| polkitd         |   2001 |
| sshd            |   2001 |
| postfix         |   2001 |
| chrony          |   2001 |
| mysql           |   2001 |
| yaya9           |   2001 |
| y7aya           |   2001 |
| ya6ya           |   2001 |
| 3yaya           |   2001 |
+-----------------+--------+
24 rows in set (0.00 sec)

root@mysqldb 15:38:  [(none)]> select name,uid,gid ,(uid+gid)/2  pjf   from db3.user  where  name="games";
+-------+------+------+---------+
| name  | uid  | gid  | pjf     |
+-------+------+------+---------+
| games |   12 |  100 | 56.0000 |
+-------+------+------+---------+
1 row in set (0.00 sec)

root@mysqldb 15:39:  [(none)]> select * from db3.user where id % 2 = 0 ;
+----+-----------------+-----+----------+------+------+---------+--------------------+---------------+
| id | name            | age | password | uid  | gid  | comment | homedir            | shell         |
+----+-----------------+-----+----------+------+------+---------+--------------------+---------------+
|  2 | bin             |  19 | A        |    1 |    1 | student | /bin               | /sbin/nologin |
|  4 | adm             |  19 | A        |    3 |    4 | student | /var/adm           | /sbin/nologin |
|  6 | sync            |  19 | A        |    5 |    0 | student | /sbin              | /bin/sync     |
|  8 | halt            |  19 | A        |    7 |    0 | student | /sbin              | /sbin/halt    |
| 10 | operator        |  19 | A        |   11 |    0 | student | /root              | /sbin/nologin |
| 12 | ftp             |  19 | A        |   14 |   50 | student | /var/ftp           | /sbin/nologin |
| 14 | systemd-network |  19 | A        |  192 |  192 | student | /                  | /sbin/nologin |
| 16 | polkitd         |  19 | A        |  999 |  998 | student | /                  | /sbin/nologin |
| 18 | postfix         |  19 | A        |   89 |   89 | student | /var/spool/postfix | /sbin/nologin |
| 20 | mysql           |  19 | A        | 1000 | 1000 | student | /home/mysql        | /sbin/nologin |
| 26 | y7aya           |  19 | NULL     | NULL | NULL | NULL    | NULL               | NULL          |
| 28 | 3yaya           |  19 | NULL     | NULL | NULL | NULL    | NULL               | NULL          |
+----+-----------------+-----+----------+------+------+---------+--------------------+---------------+
12 rows in set (0.00 sec)

root@mysqldb 15:39:  [(none)]> select name , uid  from  db3.user where  uid % 2  !=  0 ;
+----------+------+
| name     | uid  |
+----------+------+
| bin      |    1 |
| adm      |    3 |
| sync     |    5 |
| halt     |    7 |
| operator |   11 |
| nobody   |   99 |
| dbus     |   81 |
| polkitd  |  999 |
| postfix  |   89 |
+----------+------+
9 rows in set (0.00 sec)

聚集函数

求和     	sum(字段名)  
求平均数  avg(字段名)  
最大值    max(字段名) 
最小值    min(字段名)  
个数      count(字段名)

root@mysqldb 15:39:  [(none)]> select max(uid) from db3.user ;
+----------+
| max(uid) |
+----------+
|     1000 |
+----------+
1 row in set (0.00 sec)

root@mysqldb 15:41:  [(none)]> select max(uid) from db3.user  where id <= 10;
+----------+
| max(uid) |
+----------+
|       11 |
+----------+
1 row in set (0.00 sec)

root@mysqldb 15:41:  [(none)]> select min(uid) from db3.user  where id <= 10;
+----------+
| min(uid) |
+----------+
|        0 |
+----------+
1 row in set (0.00 sec)

root@mysqldb 15:41:  [(none)]> select avg(uid) from db3.user;
+----------+
| avg(uid) |
+----------+
| 180.2500 |
+----------+
1 row in set (0.00 sec)

root@mysqldb 15:41:  [(none)]> select count(name) from  db3.user where shell!="/bin/bash";
+-------------+
| count(name) |
+-------------+
|          19 |
+-------------+
1 row in set (0.00 sec)

root@mysqldb 15:41:  [(none)]> select count(*) from  db3.user;
+----------+
| count(*) |
+----------+
|       24 |
+----------+
1 row in set (0.00 sec)

root@mysqldb 15:41:  [(none)]> select min(uid) , max(gid) from db3.user;
+----------+----------+
| min(uid) | max(gid) |
+----------+----------+
|        0 |     1000 |
+----------+----------+
1 row in set (0.00 sec)

root@mysqldb 15:41:  [(none)]> select min(uid) zx , max(gid) zd from db3.user;
+------+------+
| zx   | zd   |
+------+------+
|    0 | 1000 |
+------+------+
1 row in set (0.00 sec)

查询结果 排序 order by 字段名 asc|desc

root@mysqldb 15:41:  [(none)]> select name , uid  from  db3.user  where  uid >=10 and  uid <= 800 
    -> order by uid asc;
+-----------------+------+
| name            | uid  |
+-----------------+------+
| operator        |   11 |
| games           |   12 |
| ftp             |   14 |
| sshd            |   74 |
| dbus            |   81 |
| postfix         |   89 |
| nobody          |   99 |
| systemd-network |  192 |
+-----------------+------+
8 rows in set (0.00 sec)

root@mysqldb 15:42:  [(none)]> select name , uid  from  db3.user  where  uid >=10 and  uid <= 800
    -> order by uid  desc;
+-----------------+------+
| name            | uid  |
+-----------------+------+
| systemd-network |  192 |
| nobody          |   99 |
| postfix         |   89 |
| dbus            |   81 |
| sshd            |   74 |
| ftp             |   14 |
| games           |   12 |
| operator        |   11 |
+-----------------+------+
8 rows in set (0.00 sec)

查询结果分组 group by 字段名

root@mysqldb 15:43:  [(none)]> select shell  from  db3.user where   uid >= 10  group by shell;
+---------------+
| shell         |
+---------------+
| /sbin/nologin |
+---------------+
1 row in set (0.00 sec)

root@mysqldb 15:43:  [(none)]> select shell from db3.user group by shell;
+----------------+
| shell          |
+----------------+
| NULL           |
| /bin/bash      |
| /bin/sync      |
| /sbin/halt     |
| /sbin/nologin  |
| /sbin/shutdown |
+----------------+
6 rows in set (0.00 sec)

distinct 去重显示

root@mysqldb 15:43:  [(none)]> select shell from db3.user;
+----------------+
| shell          |
+----------------+
| /bin/bash      |
| /sbin/nologin  |
| /sbin/nologin  |
| /sbin/nologin  |
| /sbin/nologin  |
| /bin/sync      |
| /sbin/shutdown |
| /sbin/halt     |
| /sbin/nologin  |
| /sbin/nologin  |
| /sbin/nologin  |
| /sbin/nologin  |
| /sbin/nologin  |
| /sbin/nologin  |
| /sbin/nologin  |
| /sbin/nologin  |
| /sbin/nologin  |
| /sbin/nologin  |
| /sbin/nologin  |
| /sbin/nologin  |
| NULL           |
| NULL           |
| NULL           |
| NULL           |
+----------------+
24 rows in set (0.00 sec)

root@mysqldb 15:44:  [(none)]> select  distinct shell from db3.user ;
+----------------+
| shell          |
+----------------+
| /bin/bash      |
| /sbin/nologin  |
| /bin/sync      |
| /sbin/shutdown |
| /sbin/halt     |
| NULL           |
+----------------+
6 rows in set (0.00 sec)

root@mysqldb 15:44:  [(none)]> select  distinct gid from db3.user;
+------+
| gid  |
+------+
|    0 |
|    1 |
|    2 |
|    4 |
|    7 |
|   12 |
|  100 |
|   50 |
|   99 |
|  192 |
|   81 |
|  998 |
|   74 |
|   89 |
|  996 |
| 1000 |
| NULL |
+------+
17 rows in set (0.00 sec)

过滤查询结果 having 条件

root@mysqldb 15:44:  [(none)]> select name from  db3.user where shell != "/bin/bash"  having  name in ("sync","games");
+-------+
| name  |
+-------+
| sync  |
| games |
+-------+
2 rows in set (0.00 sec)

root@mysqldb 15:45:  [(none)]> select  id , name from  db3.user where id >= 10   having  name is null ;
Empty set (0.00 sec)

root@mysqldb 15:45:  [(none)]> select id , name from db3.user where id >= 10 and name is null ;
Empty set (0.00 sec)

限制查询结果显示行数 limit

root@mysqldb 15:46:  [(none)]> select name , uid  , gid  from db3.user where  shell !=  "/bin/bash" limit 1;
+------+------+------+
| name | uid  | gid  |
+------+------+------+
| bin  |    1 |    1 |
+------+------+------+
1 row in set (0.00 sec)

root@mysqldb 15:46:  [(none)]> select name , uid  , gid  from db3.user where  shell !=  "/bin/bash" limit 3;
+--------+------+------+
| name   | uid  | gid  |
+--------+------+------+
| bin    |    1 |    1 |
| daemon |    2 |    2 |
| adm    |    3 |    4 |
+--------+------+------+
3 rows in set (0.00 sec)

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