一、表的连接：
连接:－－－－>内连接（相当于取交集）
mysql> select *from users;
+------+------+
| uid | name |
+------+------+
| 500 | u1 |
| 501 | u2 |
| 503 | u3 |
| 504 | u4 |
+------+------+
4 rows in set (0.00 sec)
mysql> select *from groups;
+------+------+
| gid | name |
+------+------+
| 600 | g1 |
| 601 | g2 |
| 602 | g3 |
| 603 | g4 |
+------+------+
4 rows in set (0.00 sec)
mysql> select *from u_g;
+------+------+
| uid | gid |
+------+------+
| 500 | 600 |
| 500 | 601 |
| 501 | 601 |
| 503 | 603 |
+------+------+
mysql> select users.name,groups.name from users,groups,u_g where users.uid=u_g.uid and groups.gid=u_g.gid;条件过滤
－－－－>外连接
mysql> select *from users left join u_g on users.uid=u_g.uid;左连接（会显示左边表的全部数据）
+------+------+------+------+
| uid | name | uid | gid |
+------+------+------+------+
| 500 | u1 | 500 | 600 |
| 500 | u1 | 500 | 601 |
| 501 | u2 | 501 | 601 |
| 503 | u3 | 503 | 603 |
| 504 | u4 | NULL | NULL |
+------+------+------+------+
mysql> select *from users left join u_g using(uid) where gid is null;重复的字段不显示
+------+------+------+
| uid | name | gid |
+------+------+------+
| 504 | u4 | NULL |
+------+------+------+
mysql> select *from u_g right join groups on u_g.gid=groups.gid;右连接（会显示右边表的全部数据）
+------+------+------+------+
| uid | gid | gid | name |
+------+------+------+------+
| 500 | 600 | 600 | g1 |
| 500 | 601 | 601 | g2 |
| 501 | 601 | 601 | g2 |
| NULL | NULL | 602 | g3 |
| 503 | 603 | 603 | g4 |
+------+------+------+------+
mysql> select *from u_g right join groups on u_g.gid=groups.gid where uid is not null;
+------+------+------+------+
| uid | gid | gid | name |
+------+------+------+------+
| 500 | 600 | 600 | g1 |
| 500 | 601 | 601 | g2 |
| 501 | 601 | 601 | g2 |
| 503 | 603 | 603 | g4 |
+------+------+------+------+
mysql> select *from u_g right join groups on u_g.gid=groups.gid where uid is not null group by name;分组
+------+------+------+------+
| uid | gid | gid | name |
+------+------+------+------+
| 500 | 600 | 600 | g1 |
| 500 | 601 | 601 | g2 |
| 503 | 603 | 603 | g4 |
+------+------+------+------+
mysql> select *,count(*) from u_g right join groups on u_g.gid=groups.gid where uid is not null group by name;统计
+------+------+------+------+----------+
| uid | gid | gid | name | count(*) |
+------+------+------+------+----------+
| 500 | 600 | 600 | g1 | 1 |
| 500 | 601 | 601 | g2 | 2 |
| 503 | 603 | 603 | g4 | 1 |
+------+------+------+------+----------+
3 rows in set (0.02 sec)
mysql> select *,count(*) from u_g right join groups on u_g.gid=groups.gid where uid is not null group by name having count(*)>=2;连用
+------+------+------+------+----------+
| uid | gid | gid | name | count(*) |
+------+------+------+------+----------+
| 500 | 601 | 601 | g2 | 2 |
+------+------+------+------+----------+
练习：统计每个地区的平均成绩
mysql> select *from tests;
+------+------+---------+------+
| name | sys | network | addr |
+------+------+---------+------+
| fly | 88 | 99 | bj |
| moon | 99 | 99 | bj |
| star | 78 | 100 | sy |
| sky | 100 | 100 | bj |
| join | 59 | 88 | sy |
+------+------+---------+------+
5 rows in set (0.00 sec)
mysql> select addr,avg(sys) as avg from tests group by addr;
+------+---------+
| addr | avg |
+------+---------+
| bj | 95.6667 |
| sy | 68.5000 |
+------+---------+
mysql> select addr,avg(sys+network) as avg from tests group by addr;
+------+----------+
| addr | avg |
+------+----------+
| bj | 195.0000 |
| sy | 162.5000 |
+------+----------+
－－－－－－－－－－－－－－－－－－－－－－－－－－－－－－－－－－－－－－－－－－－－－－－－－－－－－－－－－－－－－－－－－－－－
二、数据的导入与导出－－－－>数据备份
mysql> load data infile '/tem/11.txt' into table u_g fields terminated by ',' lines terminated by '\n'; 默认分割符为TAB键
mysql> create table passwd(
-> name char(20),
-> pass char(5),
-> uid int,
-> gid int,
-> des char(20),
-> home char(20),
-> bash char(20));
Query OK, 0 rows affected (0.01 sec)
mysql> load data infile '/tmp/passwd' into table passwd fields terminated by ':' enclosed by '"';双引号除外
mysql> select name ,count(name) from passwd where bash!='/bin/bash';
+------+-------------+
| name | count(name) |
+------+-------------+
| bin | 36 |
+------+-------------+
mysql> select name ,count(name) from passwd where bash!='/bin/bash' into outfile '/tmp/pass' fields terminated by ':';数据的导出
练习一百万条记录的查询：
[root@stu65 tmp]# for i in {1..1000000}
> do
> echo "$i,test$i,test@126.com" >> /tmp/name.txt
> done
mysql> create table name(
-> id int,
-> name char(20),
-> email char(30),
-> index idx_name(name));
Query OK, 0 rows affected (0.00 sec)
mysql> load data infile '/tmp/name.txt' into table name fields terminated by ',';
Query OK, 1000000 rows affected (10.56 sec)
Records: 1000000 Deleted: 0 Skipped: 0 Warnings: 0
mysql> explain select * from name where id='100'\G跟踪命令记录详细信息
*************************** 1. row ***************************
id: 1
select_type: SIMPLE
table: name
type: ALL
possible_keys: NULL
key: NULL
key_len: NULL
ref: NULL
rows: 1000000
Extra: Using where
1 row in set (0.00 sec)
mysql> explain select * from name where name='test100'\G
*************************** 1. row ***************************
id: 1
select_type: SIMPLE
table: name
type: ref
possible_keys: idx_name
key: idx_name
key_len: 21
ref: const
rows: 1
Extra: Using where
1 row in set (0.00 sec)
－－－－－－－－－－－－－－－－－－－－－－－－－－－－－－－－－－－－－－－－－－－－－－－－－－－－－－－－－－－－－－－－－－－－
三、记录复制
mysql> insert into users select uid,name from passwd;表数据导入另一个表中
mysql> alter table users add id int primary key auto_increment first;
mysql> insert into users(uid,name) select uid,name from passwd order by uid;指定列插入
－－－－－－－－－－－－－－－－－－－－－－－－－－－－－－－－－－－－－－－－－－－－－－－－－－－－－－－－－－－－－－－－－－－－
四、表复制
mysql> create table db2 select *from users;表的复制－－－－>但是不复制表的索引
mysql> create table db3 select *from users where 0=1;复制表的框架（后面接不成立的条件即可）
mysql> create table db3 like users;复制表的框架也复制主键之类
－－－－－－－－－－－－－－－－－－－－－－－－－－－－－－－－－－－－－－－－－－－－－－－－－－－－－－－－－－－－－－－－－－－－－
五、表的备份和恢复－－－－>备份工具Mysqldump（逻辑备份）
[root@stu65 tmp]# mysqldump test -uroot -p123456 > /root/test.bak.sql备份
[root@stu65 tmp]# mysql -l -uroot -p123456 < /root/test.bak.sql恢复（需要手动创建和恢复数据库同名的数据库）参数：锁定数据库
[root@stu65 tmp]# mysqldump --all-databases -uroot -p123456 > /root/alldata.bak.mysql＆＆ gzip /root/alldata.bak备份所有数据库
[root@stu65 ~]# mysqldump -B test clusz > db.sql -uroot -p123456对两个库进行备份
[root@stu65 ~]# mysqldump test passwd > users.bak.sql -uroot -p123456备份一个表
[root@stu65 ~]# mysqldump test passwd users > two.bak.sql -uroot -p123456备份两个表
[root@stu65 ~]# cat two.bak.sql | mysql test -uroot -p123456表的恢复或者在mysql中执行语句source ./two.bak.sql;
－－－－－－－－－－－－－－－－－－－－－－－－－－－－－－－－－－－－－－－－－－－－－－－－－－－－－－－－－－－－－－－－－－－－－
六、用户管理
GRANT ALL PRIVILEGES ON *.* TO 'myuser'@'%' IDENTIFIED BY 'mypassword' WITH GRANT OPTION; 授予全部权限
mysql> grant select,insert on test.* to user1@'192.168.1.%' identified by '123456';授权
mysql> grant select(uid,gid),update(id) on db1.uses_groups to user2@loaclhost;具体到表的授权
mysql> grant usage on test.* to user5;＝＝＝＝create user user6对表没有权限
mysql> drop user user3;删除用户
mysql> drop user user3@localhost;
mysql> revoke insert on test.* from user1@'192.168.1.%';撤销user1@'192.168.1.%'的insert'权限
mysql> show grants for user1@'192.168.1.%'\G查看权限
*************************** 1. row ***************************
Grants for user1@192.168.1.%: GRANT USAGE ON *.* TO 'user1'@'192.168.1.%' IDENTIFIED BY PASSWORD '*6BB4837EB74329105EE4568DDA7DC67ED2CA2AD9'
*************************** 2. row ***************************
Grants for user1@192.168.1.%: GRANT SELECT ON `test`.* TO 'user1'@'192.168.1.%'
2 rows in set (0.00 sec)
mysql> insert into mysql.user (host,user,password,select_priv) values('1921.68.1.%','user2',password('123456'),'y');手动创建mysql用户
[root@stu65 conf]# /etc/init.d/mysql修改root密码
[root@stu65 htdocs]# mysql_safe --skip-grant-table;
[root@localhost Desktop]# mysql -u root
mysql> update user set password=PASSWORD(新密码) where user='root';修改密码
mysql> flush privileges;刷新授权表
1.导出整个数据库
mysqldump -u 用户名 -p 数据库名 > 导出的文件名
mysqldump -u wcnc -p smgp_apps_wcnc > wcnc.sql
2.导出一个表
mysqldump -u 用户名 -p 数据库名 表名> 导出的文件名
mysqldump -u wcnc -p smgp_apps_wcnc users> wcnc_users.sql
3.导出一个数据库结构
mysqldump -u wcnc -p -d --add-drop-table smgp_apps_wcnc >d:wcnc_db.sql
-d 没有数据 --add-drop-table 在每个create语句之前增加一个drop table
4.导入数据库
常用source 命令
进入mysql数据库控制台，
如mysql -u root -p
mysql>use 数据库
然后使用source命令，后面参数为脚本文件(如这里用到的.sql)
mysql>source d:wcnc_db.sql （注：如果写成source d:\wcnc_db.sql，就会报语法错误）
