SQL语句
DDL：数据库定义语言（库、表的管理）
CREATE,DROP,ALTER
mysql> show databases;
+--------------------+
| Database |
+--------------------+
| information_schema | ###虚拟库，用户信息
| mysql | ###授权库，用户权限信息
| performance_schema | ###数据库性能参数
| sys | ###数据库性能参数
+--------------------+
创建数据库
mysql> CREATE database Q;
名字要求：1、区分大小写
2、不能与命令相同
3、不能纯数字、特殊符号
进入数据库
mysql> USE node1; ###进入node1
Database changed
mysql> SELECT database(); ###查看所在库
+------------+
| database() |
+------------+
| node1 |
+------------+
1 row in set (0.00 sec)
删除数据库
drop database Q;建表
mysql> create table t1 (id int);
Query OK, 0 rows affected (0.03 sec)
mysql> create table t2 (id int,name varchar(30));
Query OK, 0 rows affected (0.02 sec)
查表
mysql> show tables； ###显示表名
+-----------------+
| Tables_in_node1 |
+-----------------+
| t1 |
+-----------------+
1 row in set (0.01 sec)
mysql> desc t2； ###显示表结构
+-------+-------------+------+-----+---------+-------+
| Field | Type | Null | Key | Default | Extra |
+-------+-------------+------+-----+---------+-------+
| id | int | YES | | NULL | |
| name | varchar(30) | YES | | NULL | |
+-------+-------------+------+-----+---------+-------+
mysql> select * from t2; ###显示表内容
+------+------+
| id | name |
+------+------+
| 1 | Q |
| 2 | K |
+------+------+
2 rows in set (0.00 sec)
mysql> show create table student2\G ###显示表属性
*************************** 1. row ***************************
Table: student2
Create Table: CREATE TABLE `student2` (
`name` varchar(5) DEFAULT NULL,
`sex` enum('m','w') DEFAULT NULL,
`job` set('worker','dancer','IT','teacher') DEFAULT NULL
) ENGINE=InnoDB DEFAULT CHARSET=utf8mb4 COLLATE=utf8mb4_0900_ai_ci
1 row in set (0.00 sec)
删表
mysql> drop table t1;
Query OK, 0 rows affected (0.01 sec)TYPE类型：
一、数值类型
int——整数
unsigned-无符号型
mysql> create table test2 (int_test int unsigned,tinyint_test tinyint unsigned)
;
Query OK, 0 rows affected (0.01 sec)
mysql> desc test2
-> ;
+--------------+------------------+------+-----+---------+-------+
| Field | Type | Null | Key | Default | Extra |
+--------------+------------------+------+-----+---------+-------+
| int_test | int unsigned | YES | | NULL | |
| tinyint_test | tinyint unsigned | YES | | NULL | |
+--------------+------------------+------+-----+---------+-------+
2 rows in set (0.00 sec)
zerofill-零填充
mysql> create table test3 (id int(6) zerofill,age int(10) zerofill);
Query OK, 0 rows affected, 4 warnings (0.02 sec)
mysql> desc test3;
+-------+---------------------------+------+-----+---------+-------+
| Field | Type | Null | Key | Default | Extra |
+-------+---------------------------+------+-----+---------+-------+
| id | int(6) unsigned zerofill | YES | | NULL | |
| age | int(10) unsigned zerofill | YES | | NULL | |
+-------+---------------------------+------+-----+---------+-------+
2 rows in set (0.00 sec)
mysql> select * from test3;
+--------+------------+
| id | age |
+--------+------------+
| 000023 | 0000000078 |
+--------+------------+
1 row in set (0.00 sec)
float——小数，四舍五入
decimal——准确小数，直接放弃
mysql> create table test4 (sum float(5,3)); ###float(5位数，3位是小数)
Query OK, 0 rows affected, 1 warning (0.02 sec)
mysql> desc test4;
+-------+------------+------+-----+---------+-------+
| Field | Type | Null | Key | Default | Extra |
+-------+------------+------+-----+---------+-------+
| sum | float(5,3) | YES | | NULL | |
+-------+------------+------+-----+---------+-------+
1 row in set (0.01 sec)二、字符类型
char——255位
varchar——65535位三、枚举、集合类型
enum——单选
set——多选
mysql> create table student2 (name varchar(5),
-> sex enum('m','w'),
-> job set('worker','dancer','IT','teacher'));
Query OK, 0 rows affected (0.02 sec)
mysql> insert into student2 values('K','w','worker,dancer');
Query OK, 1 row affected (0.00 sec)
四、时间类型
date——日期
time——时间
year——年
datetime——时间日期
timestamp——自动填充时间
mysql> create table t6 (d date,t time,dt datetime);
Query OK, 0 rows affected (0.02 sec)
mysql> insert into t6 values(now(),now(),now()); ###函数now()，系统当前时间
Query OK, 1 row affected, 1 warning (0.00 sec)
mysql> select * from t6;
+------------+----------+---------------------+
| d | t | dt |
+------------+----------+---------------------+
| 2023-11-28 | 15:48:32 | 2023-11-28 15:48:32 |
+------------+----------+---------------------+
1 row in set (0.00 sec)表约束
default——默认值
not null——不能为空
unsigned——无符号
zerofill——零填充
primary key——值不能重复、不能为空
auto_increment——自动按序填写
foreign key——同步父表主键与其他子表外键
unique——值不能重复、可以为空
mysql> create table student3 (
-> id int not null,
-> name varchar(10) not null,
-> sex enum('m','w') default'm',
-> age int(3) unsigned not null;
Query OK, 0 rows affected, 1 warning (0.02 sec)
mysql> desc student3;
+-------+---------------+------+-----+---------+-------+
| Field | Type | Null | Key | Default | Extra |
+-------+---------------+------+-----+---------+-------+
| id | int | NO | | NULL | |
| name | varchar(10) | NO | | NULL | |
| sex | enum('m','w') | YES | | m | |
| age | int unsigned | NO | | NULL | |
+-------+---------------+------+-----+---------+-------+
4 rows in set (0.00 sec)
mysql> create table t1 (
-> id int primary key auto_increment, <<————
-> name varchar(10) not null,
-> sex enum('m','w') default'w');
Query OK, 0 rows affected (0.02 sec)
效果一样：
mysql> create table t1 (
-> id int auto_increment,
-> name varchar(10) not null,
-> sex enum('m','w') default'w'),
-> primary key (id)); <<————
mysql> desc t1;
+-------+---------------+------+-----+---------+----------------+
| Field | Type | Null | Key | Default | Extra |
+-------+---------------+------+-----+---------+----------------+
| id | int | NO | PRI | NULL | auto_increment |
| name | varchar(10) | NO | | NULL | |
| sex | enum('m','w') | YES | | w | |
+-------+---------------+------+-----+---------+----------------+
3 rows in set (0.00 sec)
复合主键：
mysql> create table t2(
-> id int auto_increment,
-> name varchar(10) not null,
-> sex enum('m','w') default'm',
-> primary key(id,name)); <<————
mysql> desc t2;
+-------+---------------+------+-----+---------+----------------+
| Field | Type | Null | Key | Default | Extra |
+-------+---------------+------+-----+---------+----------------+
| id | int | NO | PRI | NULL | auto_increment |
| name | varchar(10) | NO | PRI | NULL | |
| sex | enum('m','w') | YES | | m | |
+-------+---------------+------+-----+---------+----------------+
3 rows in set (0.00 sec)
外键：
mysql> create table t1 (
-> name varchar(10) primary key,
-> mail varchar(20) not null,
-> tel int(11) unsigned);
mysql> desc t1;
+-------+--------------+------+-----+---------+-------+
| Field | Type | Null | Key | Default | Extra |
+-------+--------------+------+-----+---------+-------+
| name | varchar(10) | NO | PRI | NULL | |
| mail | varchar(20) | NO | | NULL | |
| tel | int unsigned | YES | | NULL | |
+-------+--------------+------+-----+---------+-------+
3 rows in set (0.00 sec)
mysql> create table t2 (
-> id int(3) auto_increment,
-> name varchar(10) not null,
-> payroll float(8,2) not null,
-> primary key(id),
-> foreign key(name) references t1(name) on update cascade on delete cascade);
<<————
Query OK, 0 rows affected, 2 warnings (0.03 sec)
mysql> desc t2;
+---------+-------------+------+-----+---------+----------------+
| Field | Type | Null | Key | Default | Extra |
+---------+-------------+------+-----+---------+----------------+
| id | int | NO | PRI | NULL | auto_increment |
| name | varchar(10) | NO | MUL | NULL | |
| payroll | float(8,2) | NO | | NULL | |
+---------+-------------+------+-----+---------+----------------+
3 rows in set (0.00 sec)
DML：数据库操纵语言（数据的管理）
INSERT,DELETE,UPDATE
插入数据
mysql> insert into t2 values (1,"Q"); ###多个数据
Query OK, 1 row affected (0.00 sec)
mysql> insert into t2 (name) values ('C'); ###指定数据
Query OK, 1 row affected (0.01 sec)
mysql> insert into t2 values(3,'A'),(4,'B'),(5,'C');
Query OK, 3 rows affected (0.00 sec)
Records: 3 Duplicates: 0 Warnings: 0
更新数据
mysql> update t1 set sex='w' where sex='m';
Query OK, 1 row affected (0.00 sec)
Rows matched: 1 Changed: 1 Warnings: 0
mysql> update t2 set id=9 where name='C';
Query OK, 1 row affected (0.01 sec)
Rows matched: 1 Changed: 1 Warnings: 0
删除数据
mysql> delete from t1 where name='K'; ###多个数据
Query OK, 1 row affected (0.00 sec)
mysql> update t2 set id=null where name='Q'; ###指定数据
Query OK, 1 row affected (0.00 sec)
Rows matched: 1 Changed: 1 Warnings: 0
DQL：数据库查询语言
SELECT
一、简单查询
select * from t1; <<---查看所有列
mysql> select id,name from t2; <<---查看指定列
+----+------+
| id | name |
+----+------+
| 3 | H |
| 2 | K |
| 1 | Q |
+----+------+
3 rows in set (0.00 sec)
mysql> select name,payroll*9 from t2; <<---结果加减乘除
+------+-----------+
| name | payroll*9 |
+------+-----------+
| Q | 7200.00 |
| K | 6030.00 |
| H | 8100.00 |
+------+-----------+
3 rows in set (0.00 sec)
二、条件查询
=，and，or，between and，in，like
mysql> select name,mail from t1 where mail='[email protected]'; <<---单条件查询
+------+-----------+
| name | mail |
+------+-----------+
| K | [email protected] |
+------+-----------+
1 row in set (0.00 sec)
mysql> select name,payroll from t2 where id='3' and payroll>700; <<---and多条件查询
+------+---------+
| name | payroll |
+------+---------+
| H | 900.00 |
+------+---------+
1 row in set (0.00 sec)
mysql> select name,payroll from t2 where id='3' or payroll>700; <<---or多条件查询
+------+---------+
| name | payroll |
+------+---------+
| Q | 800.00 |
| H | 900.00 |
+------+---------+
2 rows in set (0.00 sec)
mysql> select name,payroll from t2 where payroll between 600 and 800; <<---两个数之间
+------+---------+
| name | payroll |
+------+---------+
| Q | 800.00 |
| K | 670.00 |
+------+---------+
2 rows in set (0.00 sec)
mysql> select name,payroll from t2 where payroll not between 600 and 800; <<---两个数之外
+------+---------+
| name | payroll |
+------+---------+
| H | 900.00 |
+------+---------+
1 row in set (0.00 sec)
mysql> select name,payroll from t2 where payroll in(800,900); <<---in多条件查询
+------+---------+
| name | payroll |
+------+---------+
| Q | 800.00 |
| H | 900.00 |
+------+---------+
2 rows in set (0.00 sec)
mysql> select name,payroll from t2 where payroll not in(800,900);
+------+---------+
| name | payroll |
+------+---------+
| K | 670.00 |
+------+---------+
1 row in set (0.00 sec)
mysql> select name,tel from t1 where tel is null; <<---查询空值
+------+------+
| name | tel |
+------+------+
| M | NULL |
+------+------+
1 row in set (0.00 sec)
mysql> select name,tel from t1 where tel is not null;
+------+------+
| name | tel |
+------+------+
| H | 789 |
| K | 456 |
| Q | 123 |
+------+------+
3 rows in set (0.00 sec)
mysql> select name,mail from t1 where mail like 'M@%'; <<---模糊查询
+------+-----------+
| name | mail |
+------+-----------+
| M | [email protected] |
+------+-----------+
1 row in set (0.00 sec)
mysql> select name,mail from t1 where mail like '__123.com'; <<---1个下划线代表一个字符
+------+-----------+
| name | mail |
+------+-----------+
| H | [email protected] |
| K | [email protected] |
| M | [email protected] |
| Q | [email protected] |
+------+-----------+
4 rows in set (0.00 sec)
三、查询排序
asc，desc，limit
mysql> select * from t2 order by payroll asc; <<---升序，默认
+----+------+---------+
| id | name | payroll |
+----+------+---------+
| 2 | K | 670.00 |
| 1 | Q | 800.00 |
| 3 | H | 900.00 |
+----+------+---------+
3 rows in set (0.00 sec)
mysql> select * from t2 order by payroll desc; <<---降序
+----+------+---------+
| id | name | payroll |
+----+------+---------+
| 3 | H | 900.00 |
| 1 | Q | 800.00 |
| 2 | K | 670.00 |
+----+------+---------+
3 rows in set (0.00 sec)
mysql> select * from t2 order by payroll limit 2; <<---前2行
+----+------+---------+
| id | name | payroll |
+----+------+---------+
| 2 | K | 670.00 |
| 1 | Q | 800.00 |
+----+------+---------+
2 rows in set (0.00 sec)
四、多表查询
mysql> select t1.name,t1.tel,t2.payroll from t1,t2 where t1.name = t2.name; <<---内连接，显示两表相同列的其他信息
+------+------+---------+
| name | tel | payroll |
+------+------+---------+
| Q | 123 | 800.00 |
| K | 456 | 670.00 |
| H | 789 | 900.00 |
+------+------+---------+
3 rows in set (0.00 sec)
mysql> select t2.id,t1.name,t1.mail,t2.payroll <<---左连接，先显示左表,再匹配
-> from t1 left join t2 ###left
-> on t1.name = t2.name; ###匹配
+------+------+-----------+---------+
| id | name | mail | payroll |
+------+------+-----------+---------+
| 3 | H | [email protected] | 900.00 |
| 2 | K | [email protected] | 670.00 |
| NULL | M | [email protected] | NULL |
| 1 | Q | [email protected] | 800.00 |
+------+------+-----------+---------+
4 rows in set (0.00 sec)
mysql> select t2.id,t1.name,t1.mail,t2.payroll <<---右连接，先显示右表,再匹配
-> from t1 right join t2 ###right
-> on t1.name = t2.name; ###匹配
+----+------+-----------+---------+
| id | name | mail | payroll |
+----+------+-----------+---------+
| 1 | Q | [email protected] | 800.00 |
| 2 | K | [email protected] | 670.00 |
| 3 | H | [email protected] | 900.00 |
+----+------+-----------+---------+
3 rows in set (0.00 sec)
mysql> select t2.id,t1.name from t1,t2; <<---交叉连接，查询结果相乘
+----+------+
| id | name |
+----+------+
| 1 | H |
| 2 | H |
| 3 | H |
| 1 | K |
| 2 | K |
| 3 | K |
| 1 | M |
| 2 | M |
| 3 | M |
| 1 | Q |
| 2 | Q |
| 3 | Q |
+----+------+
12 rows in set (0.00 sec)
五、复合使用
mysql> select t1.name,t1.mail,t2.id,t2.payroll <<---左连接+and匹配
-> from t1 left join t2
-> on t1.name =t2.name ###第一次条件匹配
-> and payroll >700; ###第二次条件匹配
+------+-----------+------+---------+
| name | mail | id | payroll |
+------+-----------+------+---------+
| H | [email protected] | 3 | 900.00 |
| K | [email protected] | NULL | NULL |
| M | [email protected] | NULL | NULL |
| Q | [email protected] | 1 | 800.00 |
+------+-----------+------+---------+
4 rows in set (0.00 sec)
mysql> select t1.name,t1.mail,t2.id,t2.payroll <<---左连接+排序
-> from t1 left join t2
-> on t1.name = t2.name ###条件匹配
-> order by id asc; ###结果排序
+------+-----------+------+---------+
| name | mail | id | payroll |
+------+-----------+------+---------+
| M | [email protected] | NULL | NULL |
| Q | [email protected] | 1 | 800.00 |
| K | [email protected] | 2 | 670.00 |
| H | [email protected] | 3 | 900.00 |
+------+-----------+------+---------+
4 rows in set (0.00 sec)
mysql> select * from t1 where name ###然后根据匹配结果显示
-> in (select name from t2 where payroll >700); ###首先条件匹配
+------+-----------+------+
| name | mail | tel |
+------+-----------+------+
| Q | [email protected] | 123 |
| H | [email protected] | 789 |
+------+-----------+------+
2 rows in set (0.00 sec)
mysql> select * from t1 where
-> exists (select * from t2 where payroll >1000); ###条件不成立，输出空
Empty set (0.00 sec)
mysql> select * from t1 where
-> exists (select * from t2 where payroll >800); ###条件成立，执行父句
+------+-----------+------+
| name | mail | tel |
+------+-----------+------+
| H | [email protected] | 789 |
| K | [email protected] | 456 |
| M | [email protected] | NULL |
| Q | [email protected] | 123 |
+------+-----------+------+
4 rows in set (0.00 sec)
DCL：数据库控制语言（权限管理）
GRANT,REVOKE
创建用户
mysql> create user tom@'localhost' identified by '[email protected]';
Query OK, 0 rows affected (0.01 sec)
mysql> select * from mysql.user\G; ###查看用户
删除用户
mysql> drop user tom@'localhost';
Query OK, 0 rows affected (0.01 sec)
修改密码
mysql> alter user 'root'@'localhost' identified by 'JKzone@123456';
Query OK, 0 rows affected (0.01 sec)
mysql> flush privileges; ###加载配置
Query OK, 0 rows affected (0.00 sec)
登录参数
[root@node1 ~]# mysql -uroot -p -P 3306 ###指定端口
Enter password:
[root@node1 ~]# mysql -uroot -p school ###指定数据库
Enter password:
[root@node1 ~]# mysql -utom -p -h 192.168.1.2; ###远程登录
Enter password:
[root@node1 ~]# mysql -uroot -p'JKzone@123' -e "show databases;" <<---不登录执行命令
mysql: [Warning] Using a password on the command line interface can be insecure.
+--------------------+
| Database |
+--------------------+
| information_schema |
| mysql |
| node1 |
| performance_schema |
| school |
| sys |
+--------------------+
授权管理
mysql> grant all on node1.* to tom@'localhost'; ###授权本地登录，管理node1库
Query OK, 0 rows affected (0.01 sec)
mysql> grant all on node1.* to tom@'192.168.1.%'; ###个别网段登录
Query OK, 0 rows affected (0.01 sec)
mysql> grant select,update on school.test3 to tom@'localhost'; ###指定查询、更新权限
Query OK, 0 rows affected (0.00 sec)
mysql> grant select(id,age) on school.test3 to tom@'localhost'; ###指定列权限
Query OK, 0 rows affected (0.00 sec)
查看授权
mysql> show grants\G <<---当前用户
*************************** 1. row ***************************
Grants for [email protected].%: GRANT USAGE ON *.* TO `tom`@`112.74.52.%`
1 row in set (0.00 sec)
mysql> show grants for mary@'localhost'; <<---指定用户
+-------------------------------------------------------------+
| Grants for mary@localhost |
+-------------------------------------------------------------+
| GRANT USAGE ON *.* TO `mary`@`localhost` |
| GRANT ALL PRIVILEGES ON `school`.`t2` TO `mary`@`localhost` |
+-------------------------------------------------------------+
2 rows in set (0.00 sec)
回收授权
mysql> revoke all on school.t2 from mary@'localhost';
Query OK, 0 rows affected (0.00 sec)