MySQL基本操作命令(DDL、DML、DQL、DCL)
前言
- MySQL 是最流行的关系型数据库管理系统,在 WEB 应用方面 MySQL 是最好的 RDBMS(Relational
Database Management System:关系数据库管理系统)应用软件之一
- 最早MySQL数据,瑞典AB公司开发的一款开源型的关系型数据库。随着时间的推移,瑞典AB公司把MySQL数据库转让给Sun公司(Java语言的创始公司)后来,Sun公司经营不善,又把MySQL数据库转让给甲骨文公司(Oracle数据库)。MySQL 是一种关联数据库管理系统,关联数据库将数据保存在不同的表中,而不是将所有数据放在一个大仓库内,这样就增加了速度并提高了灵活性。
一:数据库基本操作命令
1.1:mysql查看数据库结构
-
查看数据库结构
-
创建及删除库和表
-
管理表的记录
1.2:查看数据库信息
- show databases
mysql> show databases;
+--------------------+
| Database |
+--------------------+
| information_schema |
| mysql |
| performance_schema |
| sys |
+--------------------+
4 rows in set (0.00 sec)
1.3:查看数据库中的数据表信息
- use 数据库名
- show tables
mysql> use mysql; '进入mysql数据库中'
Reading table information for completion of table and column names
You can turn off this feature to get a quicker startup with -A
Database changed
mysql> show tables;
+---------------------------+
| Tables_in_mysql |
+---------------------------+
| columns_priv |
| db |
| engine_cost |
| event |
...省略内容
1.4:显示数据表的结构(字段)
- describe [数据库名.]表名
mysql> describe user; '也可以使用desc user;'
+------------------------+-----------------------------------+------+-----+-----------------------+-------+
| Field | Type | Null | Key | Default | Extra |
+------------------------+-----------------------------------+------+-----+-----------------------+-------+
| Host | char(60) | NO | PRI | | |
二:SQL操作管理命令
2.1:SQL语言概述
- SQL语言
- 是Structured Query Language的缩写,及结构化查询语言
- 是关系型数据库的标准语言
- 用于维护管理数据库,如数据查询,数据更新,访问控制,对象管理等功能
- SQL分类
- DDL:数据定义语言
- DML:数据操纵语言
- DQL:数据查询语言
- DCL:数据控制语言
2.2:DDL操作命令
2.2.1:创建数据库和表
-
DDL语句用于创建数据库对象,如库,表,索引等
-
使用DDL语句新建库、表
2.2.2:DDL语句创建库、表的命令
- 创建数据库:create database 数据库名
- 创建数据表:create table 表名(字段定义…)
mysql> create database school;
Query OK, 1 row affected (0.00 sec)
mysql> use school;
Database changed
mysql> create table info (id int(3) not null primary key auto_increment,name varchar(10) not null,score decimal(5,2),address varchar(50) default '未知');
Query OK, 0 rows affected (0.02 sec)
'info表名','not null设置不为空','primary key主键','auto_increment自动增长'
2.2.3:DDL语句删除库,表的命令
-
删除指定的数据表:drop table [数据库名.]表名
-
删除指定的数据库:drop database 数据库名
mysql> drop table info; '删除表'
Query OK, 0 rows affected (0.00 sec)
mysql> drop database shcool; '删除库'
Query OK, 0 rows affected (0.00 sec)
2.3:DML操作命令
2.3.1:DML语句的作用
- DML语句用于对表中的数据进行管理
- 包括以下操作
- insert:插入新数据
- update:更新原有数据
- delete:删除不需要的数据
2.3.2:向数据表中插入新的数据记录命令
mysql> use school '进入school数据库'
Reading table information for completion of table and column names
You can turn off this feature to get a quicker startup with -A
Database changed
mysql> select * from info; '查看表中数据'
Empty set (0.00 sec)
mysql> show tables; '查看表'
+------------------+
| Tables_in_school |
+------------------+
| info |
+------------------+
1 row in set (0.00 sec)
mysql> desc info; '查看表结构'
+---------+--------------+------+-----+---------+----------------+
| Field | Type | Null | Key | Default | Extra |
+---------+--------------+------+-----+---------+----------------+
| id | int(3) | NO | PRI | NULL | auto_increment |
| name | varchar(10) | NO | | NULL | |
| score | decimal(5,2) | YES | | NULL | |
| address | varchar(50) | YES | | 未知 | |
+---------+--------------+------+-----+---------+----------------+
4 rows in set (0.00 sec)
mysql> insert into info (id,name,score,address) values (1,'zhangsan',88.5,'nanjing'); '插入新的数据记录'
Query OK, 1 row affected (0.00 sec)
mysql> select * from info;
+----+----------+-------+---------+
| id | name | score | address |
+----+----------+-------+---------+
| 1 | zhangsan | 88.50 | nanjing |
+----+----------+-------+---------+
1 row in set (0.00 sec)
mysql> insert into info values (2,'lisi',90,'beijing'),(3,'wangwu',77,'hangzhou');
Query OK, 2 rows affected (0.00 sec)
Records: 2 Duplicates: 0 Warnings: 0
'如果不加字段名,默认是所有字段,并且是按照从左往右'
mysql> select * from info;
+----+----------+-------+----------+
| id | name | score | address |
+----+----------+-------+----------+
| 1 | zhangsan | 88.50 | nanjing |
| 2 | lisi | 90.00 | beijing |
| 3 | wangwu | 77.00 | hangzhou |
+----+----------+-------+----------+
3 rows in set (0.00 sec)
mysql> select * from info where score > 80; '筛选出80分以上的数据'
+----+----------+-------+---------+
| id | name | score | address |
+----+----------+-------+---------+
| 1 | zhangsan | 88.50 | nanjing |
| 2 | lisi | 90.00 | beijing |
+----+----------+-------+---------+
2 rows in set (0.00 sec)
mysql> create table tmp as select * from info where score > 80; '筛选出80分以上的并导入进新的表中'
Query OK, 2 rows affected (0.01 sec)
Records: 2 Duplicates: 0 Warnings: 0
2.3.3:向表中添加字段
mysql> alter table sibiao add (id int(3) not null primary key auto_increment);
2.3.4:修改,更新数据表中的数据记录的命令
- update 表名 set 字段名 1=值1[,字段名2=值2] where条件表达式
mysql> update info set score=66 where name='zhangsan'; '修改张三的分数为66'
Query OK, 1 row affected (0.00 sec)
Rows matched: 1 Changed: 1 Warnings: 0
mysql> select * from info;
+----+----------+-------+----------+
| id | name | score | address |
+----+----------+-------+----------+
| 1 | zhangsan | 66.00 | nanjing |
| 2 | lisi | 90.00 | beijing |
| 3 | wangwu | 77.00 | hangzhou |
+----+----------+-------+----------+
3 rows in set (0.00 sec)
mysql> update info set name='zhaoliu'; '修改所有id的name'
2.3.5:在数据表中删除指定的数据记录命令
- delete from 表名 where 条件表达式
mysql> select * from info;
+----+----------+-------+----------+
| id | name | score | address |
+----+----------+-------+----------+
| 1 | zhangsan | 66.00 | nanjing |
| 2 | lisi | 90.00 | beijing |
| 3 | wangwu | 77.00 | hangzhou |
+----+----------+-------+----------+
3 rows in set (0.00 sec)
mysql> delete from info where score >= 90;
Query OK, 1 row affected (0.00 sec)
mysql> select * from info;
+----+----------+-------+----------+
| id | name | score | address |
+----+----------+-------+----------+
| 1 | zhangsan | 66.00 | nanjing |
| 3 | wangwu | 77.00 | hangzhou |
+----+----------+-------+----------+
2 rows in set (0.00 sec)
- 不带where条件的语句表示删除表中所有记录(高危操作)
mysql> delete from info;
Query OK, 4 rows affected (0.00 sec)
mysql> select * from info;
Empty set (0.00 sec)
2.3.6:查看表结构命令
mysql> desc info;
+---------+--------------+------+-----+---------+----------------+
| Field | Type | Null | Key | Default | Extra |
+---------+--------------+------+-----+---------+----------------+
| id | int(3) | NO | PRI | NULL | auto_increment |
| name | varchar(10) | NO | | NULL | |
| score | decimal(5,2) | YES | | NULL | |
| address | varchar(50) | YES | | 未知 | |
+---------+--------------+------+-----+---------+----------------+
4 rows in set (0.00 sec)
2.2.7:修改用户登录mysql的密码
mysql> update mysql.user set authentication_string=password('123456') where user='root';
[root@localhost ~]# vim /etc/my.cnf
skip-grant-tables '在[mysqld]下添加'
[root@localhost ~]# systemctl restart mysqld
[root@localhost ~]# mysql -uroot -p '输入密码123456'
2.4:DQL操作命令
2.4.1:DQL语句的作用
- DQL是数据查询语句,只有一条:select
- 用于从数据表中查找符合条件的数据记录
2.4.2:不指定条件查询命令
- select字段名1,字段名2…from表名
mysql> select name from info;
+----------+
| name |
+----------+
| zhangsan |
| wangwu |
+----------+
2 rows in set (0.00 sec)
mysql> select name,score from info;
+----------+-------+
| name | score |
+----------+-------+
| zhangsan | 66.00 |
| wangwu | 77.00 |
+----------+-------+
2 rows in set (0.00 sec)
2.4.3:指定条件查询的命令
- select字段名1,字段名2…from表名 WHERE 条件表达式
mysql> select name from info where id=1 or id=3;
+----------+
| name |
+----------+
| zhangsan |
| wangwu |
+----------+
2 rows in set (0.00 sec)
2.5:DCL操作命令
2.5.1:DCL语句的作用
- 设置或查看用户的权限,或者创建用户
2.5.2:设置用户权限的命令
- 若用户已存在,则更改用户密码
- 若用户不存在,则新建用户
- grant 权限列表 on 数据库名.表名 to 用户名@来源地址 identified by ‘密码′
mysql> grant all privileges on *.* to 'root'@'%' identified by 'abc123' with grant option;
'all privileges:所有权限,%:所有终端'
Query OK, 0 rows affected, 1 warning (0.00 sec)
2.5.3:查看用户权限的命令
- show grants for 用户名@来源地址
mysql> show grants;
+---------------------------------------------------------------------+
| Grants for root@localhost |
+---------------------------------------------------------------------+
| GRANT ALL PRIVILEGES ON *.* TO 'root'@'localhost' WITH GRANT OPTION |
| GRANT PROXY ON ''@'' TO 'root'@'localhost' WITH GRANT OPTION |
+---------------------------------------------------------------------+
2 rows in set (0.00 sec)
mysql> show grants for 'root'@'localhost';
+---------------------------------------------------------------------+
| Grants for root@localhost |
+---------------------------------------------------------------------+
| GRANT ALL PRIVILEGES ON *.* TO 'root'@'localhost' WITH GRANT OPTION |
| GRANT PROXY ON ''@'' TO 'root'@'localhost' WITH GRANT OPTION |
+---------------------------------------------------------------------+
2 rows in set (0.00 sec)
2.5.4:撤销用户权限的命令
- revoke 权限列表 on 数据库名.表名 from 用户名@来源地址
mysql> show grants;
+---------------------------------------------------------------------+
| Grants for root@localhost |
+---------------------------------------------------------------------+
| GRANT ALL PRIVILEGES ON *.* TO 'root'@'localhost' WITH GRANT OPTION |
| GRANT PROXY ON ''@'' TO 'root'@'localhost' WITH GRANT OPTION |
+---------------------------------------------------------------------+
2 rows in set (0.00 sec)
mysql> revoke all on *.* from 'root'@'localhost';
Query OK, 0 rows affected (0.00 sec)
mysql> show grants for 'root'@'localhost';
+--------------------------------------------------------------+
| Grants for root@localhost |
+--------------------------------------------------------------+
| GRANT USAGE ON *.* TO 'root'@'localhost' WITH GRANT OPTION |
| GRANT PROXY ON ''@'' TO 'root'@'localhost' WITH GRANT OPTION |
+--------------------------------------------------------------+
2 rows in set (0.00 sec)
三:数据库高级操作
3.1:清空表
-
delete from tablename
-
truncate table tablename
mysql> delete from tmp;
Query OK, 1 row affected (0.00 sec)
mysql> select * from tmp;
Empty set (0.00 sec)
3.2:临时表
临时建立的表,用于保存一些临时数据,不会长期存在(连接断开,临时表被删除)
mysql> create temporary table temp_info (id int(4) not null auto_increment,name varchar(10) not null,hobbby varchar(10) not null,primary key(id))engine=innodb default charset=utf8;
Query OK, 0 rows affected (0.00 sec)
mysql> desc temp_info;
+-------+-------------+------+-----+---------+----------------+
| Field | Type | Null | Key | Default | Extra |
+-------+-------------+------+-----+---------+----------------+
| id | int(4) | NO | PRI | NULL | auto_increment |
| name | varchar(10) | NO | | NULL | |
| hobby | varchar(10) | NO | | NULL | |
+-------+-------------+------+-----+---------+----------------+
3 rows in set (0.00 sec)
mysql> show tables; '没有看到临时表,因为是放在内存当中'
+------------------+
| Tables_in_school |
+------------------+
| info |
| tmp |
+------------------+
2 rows in set (0.00 sec)
'退出,重新进,临时表没有了'
3.3:克隆表
- 直接克隆(一气呵成)
mysql> create table kelong as select * from info; '克隆表结构和数据'
Query OK, 2 rows affected (0.01 sec)
Records: 2 Duplicates: 0 Warnings: 0
mysql> show tables;
+------------------+
| Tables_in_school |
+------------------+
| info |
| kelong |
| tmp |
+------------------+
3 rows in set (0.00 sec)
- like方法
从表完整复制结构生成新表,再导入数据
mysql> create table k like info; '相比较like不能克隆表中的数据'
Query OK, 0 rows affected (0.02 sec)
mysql> show tables;
+------------------+
| Tables_in_school |
+------------------+
| info |
| k |
| kelong |
| tmp |
+------------------+
4 rows in set (0.00 sec)
mysql> select * from k;
Empty set (0.00 sec)
mysql> insert into k select * from info;
Query OK, 2 rows affected (0.00 sec)
Records: 2 Duplicates: 0 Warnings: 0
mysql> select * from k;
+----+----------+-------+----------+
| id | name | score | address |
+----+----------+-------+----------+
| 1 | zhangsan | 66.00 | nanjing |
| 3 | wangwu | 77.00 | hangzhou |
+----+----------+-------+----------+
2 rows in set (0.00 sec)
- show create table方法
mysql> show create table info\G;
*************************** 1. row ***************************
Table: info
Create Table: CREATE TABLE "info" (
"id" int(3) NOT NULL AUTO_INCREMENT,
"name" varchar(10) NOT NULL,
"score" decimal(5,2) DEFAULT NULL,
"address" varchar(50) DEFAULT '未知',
PRIMARY KEY ("id")
) ENGINE=InnoDB AUTO_INCREMENT=4 DEFAULT CHARSET=utf8
1 row in set (0.00 sec)
ERROR:
No query specified
mysql> create table test (id int(3) not null primary key auto_increment,name varchar(10) not null,score decimal(5,2),address varchar(50) default '未知');
Query OK, 0 rows affected (0.01 sec)
mysql> insert into test select * from info;
Query OK, 2 rows affected (0.00 sec)
Records: 2 Duplicates: 0 Warnings: 0
'先查看info表完整结构,根据此结构创建名字不同结构相同的表test,再导入数据'