Linux——MySQL数据表操作

其他 2021-01-28 00:01:45 阅读次数: 0

一、数据表创建

创建数据库、数据表、插入数据

mysql> show databases;
+--------------------+
| Database           |
+--------------------+
| information_schema |
| mysql              |
| performance_schema |
| sys                |
| user               |
+--------------------+
5 rows in set (0.00 sec)

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

mysql> use shuju;
Database changed
mysql> create table t1 (id int(11),name varchar(25),deptid int(11),salary float);
Query OK, 0 rows affected (0.11 sec)

mysql> show tables;
+-----------------+
| Tables_in_shuju |
+-----------------+
| t1              |
+-----------------+
1 row in set (0.00 sec)

mysql> insert into t1 (id,name,deptid,salary) values (1,'zhangsan','1','10000');
Query OK, 1 row affected (0.01 sec)

mysql> select * from t1;
+------+----------+--------+--------+
| id   | name     | deptid | salary |
+------+----------+--------+--------+
|    1 | zhangsan |      1 |  10000 |
+------+----------+--------+--------+
1 row in set (0.00 sec)

二、约束策略

2.1 主键约束

PS：主键约束要求主键列的数据唯一，并且不允许为空。

2.1.1 单字段主键

mysql> create table t2 
    -> (
    -> id int (11) primary key,
    -> name varchar(25),
    -> deptid int(11),
    -> salary float
    -> );
Query OK, 0 rows affected (0.36 sec)

2.1.2 尾端指定主键

PS：在定义完所有列之后指定主键

mysql> create table t3 
    -> (
    -> id int(11),
    -> name varchar(25),
    -> deptid int (11),
    -> salary float,
    -> primary key (id)
    -> );
Query OK, 0 rows affected (0.01 sec)

2.1.3 多字段联合主键

PS：在定义完列表之后统一指定主键

mysql> create table t4
    -> (
    -> id int(11),
    -> name varchar(25),
    -> deptid int (11),
    -> salary float,
    -> primary key (id,name,deptid)
    -> );
Query OK, 0 rows affected (0.00 sec)

2.2 外键约束

PS：外键用来在两个表数据之间建立连接，它可以是一列或者多列

2.2.1 创建外键约束

mysql> create table tb_t1
    -> (
    -> id int(11) primary key,
    -> name varchar(22) not null,
    -> location varchar(50)
    -> );
Query OK, 0 rows affected (0.00 sec)

mysql> create table t5 
    -> (
    -> id int (11) primary key,
    -> name varchar (25),
    -> deptid int(11),
    -> salary float,
    -> constraint tb_t1_t5 foreign key(deptid) references tb_t1(id)
    -> );
Query OK, 0 rows affected (0.00 sec)

2.2.2 删除表的外键约束

mysql> create table test
    -> (
    -> id int (11) primary key,
    -> name varchar(25),
    -> deptid int(11),
    -> salary float,
    -> constraint fk_test_tb_t1 foreign key (deptid) references tb_t1(id)
    -> );
Query OK, 0 rows affected (0.01 sec)

mysql> show create table test\G
*************************** 1. row ***************************
       Table: test
Create Table: CREATE TABLE `test` (
  `id` int(11) NOT NULL,
  `name` varchar(25) DEFAULT NULL,
  `deptid` int(11) DEFAULT NULL,
  `salary` float DEFAULT NULL,
  PRIMARY KEY (`id`),
  KEY `fk_test_tb_t1` (`deptid`),
  CONSTRAINT `fk_test_tb_t1` FOREIGN KEY (`deptid`) REFERENCES `tb_t1` (`id`)
) ENGINE=InnoDB DEFAULT CHARSET=utf8
1 row in set (0.00 sec)

mysql> alter table test drop foreign key fk_test_tb_t1;
Query OK, 0 rows affected (0.00 sec)
Records: 0  Duplicates: 0  Warnings: 0

mysql> show create table test\G
*************************** 1. row ***************************
       Table: test
Create Table: CREATE TABLE `test` (
  `id` int(11) NOT NULL,
  `name` varchar(25) DEFAULT NULL,
  `deptid` int(11) DEFAULT NULL,
  `salary` float DEFAULT NULL,
  PRIMARY KEY (`id`),
  KEY `fk_test_tb_t1` (`deptid`)
) ENGINE=InnoDB DEFAULT CHARSET=utf8
1 row in set (0.00 sec)

2.3 非空约束

PS：非空约束指字段的值不能为空

mysql> create table t6
    -> (
    -> id int(11) primary key ,
    -> name varchar(25) not null,
    -> deptid int (11),
    -> salary float
    -> );
Query OK, 0 rows affected (0.00 sec)

2.4 默认约束

PS：默认约束指定某列的默认值。

mysql> create table t7
    -> (
    -> id int(11) primary key,
    -> name varchar (25) not null,
    -> deptid int (11) default 1111,
    -> salary float,
    -> info varchar(50)
    -> );
Query OK, 0 rows affected (0.01 sec)

验证：
mysql> insert into t7(id,name,salary,info) values(1,'zhansan','12','112');
Query OK, 1 row affected (0.00 sec)

mysql> select * from t7;
+----+---------+--------+--------+------+
| id | name    | deptid | salary | info |
+----+---------+--------+--------+------+
|  1 | zhansan |   1111 |     12 | 112  |
+----+---------+--------+--------+------+
1 row in set (0.00 sec)

2.5 设置表的属性值自动增加

2.5.1 创建表

mysql> create table t8
    -> (
    -> id int(11) primary key auto_increment,
    -> name varchar(25) not null,
    -> deptid int (11),
    -> salary float
    -> );
Query OK, 0 rows affected (0.00 sec)

2.5.2 插入数据

mysql> insert into t8 
    -> (name,salary)
    -> values('lucy',1000),('wangwu',1200),('zhangsan',1500);
Query OK, 3 rows affected (0.00 sec)
Records: 3  Duplicates: 0  Warnings: 0

2.5.3 查看

mysql> select * from t8;
+----+----------+--------+--------+
| id | name     | deptid | salary |
+----+----------+--------+--------+
|  1 | lucy     |   NULL |   1000 |
|  2 | wangwu   |   NULL |   1200 |
|  3 | zhangsan |   NULL |   1500 |
+----+----------+--------+--------+
3 rows in set (0.00 sec)

2.6 唯一约束

  • unique：独特的，独一无二。
mysql> create table tb_t2
    -> (
    -> id int (11) primary key,
    -> name varchar(22),
    -> location varchar(50),
    -> constraint sth unique(name)
    -> );
Query OK, 0 rows affected (0.00 sec)

三 、查看数据表结构

3.1 查看表的基本结构

mysql> describe t1;
+--------+-------------+------+-----+---------+-------+
| Field  | Type        | Null | Key | Default | Extra |
+--------+-------------+------+-----+---------+-------+
| id     | int(11)     | YES  |     | NULL    |       |
| name   | varchar(25) | YES  |     | NULL    |       |
| deptid | int(11)     | YES  |     | NULL    |       |
| salary | float       | YES  |     | NULL    |       |
+--------+-------------+------+-----+---------+-------+
4 rows in set (0.01 sec)

或者

mysql> desc t1;
+--------+-------------+------+-----+---------+-------+
| Field  | Type        | Null | Key | Default | Extra |
+--------+-------------+------+-----+---------+-------+
| id     | int(11)     | YES  |     | NULL    |       |
| name   | varchar(25) | YES  |     | NULL    |       |
| deptid | int(11)     | YES  |     | NULL    |       |
| salary | float       | YES  |     | NULL    |       |
+--------+-------------+------+-----+---------+-------+
4 rows in set (0.00 sec)

3.2 查看表详细结构

mysql> show create table t1\G
*************************** 1. row ***************************
       Table: t1
Create Table: CREATE TABLE `t1` (
  `id` int(11) DEFAULT NULL,
  `name` varchar(25) DEFAULT NULL,
  `deptid` int(11) DEFAULT NULL,
  `salary` float DEFAULT NULL
) ENGINE=InnoDB DEFAULT CHARSET=utf8
1 row in set (0.00 sec)

四、修改数据表

4.1 修改表名

mysql> show tables;
+-----------------+
| Tables_in_shuju |
+-----------------+
| t1              |
| t2              |
| t3              |
| t4              |
| t5              |
| t6              |
| t7              |
| t8              |
| tb_t1           |
| tb_t2           |
+-----------------+
10 rows in set (0.00 sec)

mysql> alter table t3 rename tb_t3;
Query OK, 0 rows affected (0.01 sec)

mysql> show tables like 'tb_t3';
+-------------------------+
| Tables_in_shuju (tb_t3) |
+-------------------------+
| tb_t3                   |
+-------------------------+
1 row in set (0.00 sec)

4.2 修改字段的数据类型

查看表

mysql> desc tb_t1;
+----------+-------------+------+-----+---------+-------+
| Field    | Type        | Null | Key | Default | Extra |
+----------+-------------+------+-----+---------+-------+
| id       | int(11)     | NO   | PRI | NULL    |       |
| name     | varchar(22) | NO   |     | NULL    |       |
| location | varchar(50) | YES  |     | NULL    |       |
+----------+-------------+------+-----+---------+-------+
3 rows in set (0.00 sec)

修改字段的数据类型

mysql> alter table tb_t1 modify name varchar(30);
Query OK, 0 rows affected (0.11 sec)
Records: 0  Duplicates: 0  Warnings: 0

mysql> desc tb_t1;
+----------+-------------+------+-----+---------+-------+
| Field    | Type        | Null | Key | Default | Extra |
+----------+-------------+------+-----+---------+-------+
| id       | int(11)     | NO   | PRI | NULL    |       |
| name     | varchar(30) | YES  |     | NULL    |       |
| location | varchar(50) | YES  |     | NULL    |       |
+----------+-------------+------+-----+---------+-------+
3 rows in set (0.00 sec)

4.3 修改字段名

  • change ：替换为
mysql> alter table tb_t1 change location local varchar (50);
Query OK, 0 rows affected (0.00 sec)
Records: 0  Duplicates: 0  Warnings: 0

mysql> desc tb_t1;
+-------+-------------+------+-----+---------+-------+
| Field | Type        | Null | Key | Default | Extra |
+-------+-------------+------+-----+---------+-------+
| id    | int(11)     | NO   | PRI | NULL    |       |
| name  | varchar(30) | YES  |     | NULL    |       |
| local | varchar(50) | YES  |     | NULL    |       |
+-------+-------------+------+-----+---------+-------+
3 rows in set (0.00 sec)

4.4 添加字段

  • add：添加
  • first：首端，第一个
  • after：最后，或者什么什么的后面一个
mysql> alter table tb_t1 add columen1 varchar (12) not null;
Query OK, 0 rows affected (0.01 sec)
Records: 0  Duplicates: 0  Warnings: 0

mysql> desc tb_t1;
+----------+-------------+------+-----+---------+-------+
| Field    | Type        | Null | Key | Default | Extra |
+----------+-------------+------+-----+---------+-------+
| id       | int(11)     | NO   | PRI | NULL    |       |
| name     | varchar(30) | YES  |     | NULL    |       |
| local    | varchar(50) | YES  |     | NULL    |       |
| columen1 | varchar(12) | NO   |     | NULL    |       |
+----------+-------------+------+-----+---------+-------+
4 rows in set (0.00 sec)

或者

mysql> alter table tb_t1 add column2 int(11) first;
Query OK, 0 rows affected (0.02 sec)
Records: 0  Duplicates: 0  Warnings: 0

mysql> desc tb_t1;
+----------+-------------+------+-----+---------+-------+
| Field    | Type        | Null | Key | Default | Extra |
+----------+-------------+------+-----+---------+-------+
| column2  | int(11)     | YES  |     | NULL    |       |
| id       | int(11)     | NO   | PRI | NULL    |       |
| name     | varchar(30) | YES  |     | NULL    |       |
| local    | varchar(50) | YES  |     | NULL    |       |
| columen1 | varchar(12) | NO   |     | NULL    |       |
+----------+-------------+------+-----+---------+-------+
5 rows in set (0.00 sec)

或者

mysql> alter table tb_t1 add column3 int(11) after name;
Query OK, 0 rows affected (0.01 sec)
Records: 0  Duplicates: 0  Warnings: 0

mysql> desc tb_t1;
+----------+-------------+------+-----+---------+-------+
| Field    | Type        | Null | Key | Default | Extra |
+----------+-------------+------+-----+---------+-------+
| column2  | int(11)     | YES  |     | NULL    |       |
| id       | int(11)     | NO   | PRI | NULL    |       |
| name     | varchar(30) | YES  |     | NULL    |       |
| column3  | int(11)     | YES  |     | NULL    |       |
| local    | varchar(50) | YES  |     | NULL    |       |
| columen1 | varchar(12) | NO   |     | NULL    |       |
+----------+-------------+------+-----+---------+-------+
6 rows in set (0.00 sec)

4.5 删除字段

mysql> alter table tb_t1 drop column2 ;
Query OK, 0 rows affected (0.01 sec)
Records: 0  Duplicates: 0  Warnings: 0

mysql> desc tb_t1;
+----------+-------------+------+-----+---------+-------+
| Field    | Type        | Null | Key | Default | Extra |
+----------+-------------+------+-----+---------+-------+
| id       | int(11)     | NO   | PRI | NULL    |       |
| name     | varchar(30) | YES  |     | NULL    |       |
| column3  | int(11)     | YES  |     | NULL    |       |
| local    | varchar(50) | YES  |     | NULL    |       |
| columen1 | varchar(12) | NO   |     | NULL    |       |
+----------+-------------+------+-----+---------+-------+
5 rows in set (0.00 sec)

4.6 修改字段的排列位置

mysql> alter table tb_t1 modify columen1 varchar(12) first;
Query OK, 0 rows affected (0.01 sec)
Records: 0  Duplicates: 0  Warnings: 0

mysql> desc tb_t1;
+----------+-------------+------+-----+---------+-------+
| Field    | Type        | Null | Key | Default | Extra |
+----------+-------------+------+-----+---------+-------+
| columen1 | varchar(12) | YES  |     | NULL    |       |
| id       | int(11)     | NO   | PRI | NULL    |       |
| name     | varchar(30) | YES  |     | NULL    |       |
| column3  | int(11)     | YES  |     | NULL    |       |
| local    | varchar(50) | YES  |     | NULL    |       |
+----------+-------------+------+-----+---------+-------+
5 rows in set (0.00 sec)

或者

mysql> alter table tb_t1 modify columen1 varchar(12) after local;
Query OK, 0 rows affected (0.01 sec)
Records: 0  Duplicates: 0  Warnings: 0

mysql> desc tb_t1;
+----------+-------------+------+-----+---------+-------+
| Field    | Type        | Null | Key | Default | Extra |
+----------+-------------+------+-----+---------+-------+
| id       | int(11)     | NO   | PRI | NULL    |       |
| name     | varchar(30) | YES  |     | NULL    |       |
| column3  | int(11)     | YES  |     | NULL    |       |
| local    | varchar(50) | YES  |     | NULL    |       |
| columen1 | varchar(12) | YES  |     | NULL    |       |
+----------+-------------+------+-----+---------+-------+
5 rows in set (0.00 sec)

4.7 更改表的存储引擎

mysql> show create table tb_t3\G
*************************** 1. row ***************************
       Table: tb_t3
Create Table: CREATE TABLE `tb_t3` (
  `id` int(11) NOT NULL,
  `name` varchar(25) DEFAULT NULL,
  `deptid` int(11) DEFAULT NULL,
  `salary` float DEFAULT NULL,
  PRIMARY KEY (`id`)
) ENGINE=InnoDB DEFAULT CHARSET=utf8
1 row in set (0.00 sec)

mysql> alter table tb_t3 engine=myisam;
Query OK, 0 rows affected (0.01 sec)
Records: 0  Duplicates: 0  Warnings: 0

mysql> show create table tb_t3\G
*************************** 1. row ***************************
       Table: tb_t3
Create Table: CREATE TABLE `tb_t3` (
  `id` int(11) NOT NULL,
  `name` varchar(25) DEFAULT NULL,
  `deptid` int(11) DEFAULT NULL,
  `salary` float DEFAULT NULL,
  PRIMARY KEY (`id`)
) ENGINE=MyISAM DEFAULT CHARSET=utf8
1 row in set (0.00 sec)

五、删除数据表

5.1 删除没有被关联的表

mysql> show tables;
+-----------------+
| Tables_in_shuju |
+-----------------+
| t1              |
| t2              |
| t4              |
| t5              |
| t6              |
| t7              |
| t8              |
| tb_t1           |
| tb_t2           |
| tb_t3           |
| test            |
+-----------------+
11 rows in set (0.00 sec)

mysql> drop table if exists tb_t2;
Query OK, 0 rows affected (0.00 sec)

5.2 删除被其他表关联的主表

5.2.1 创建表

mysql> create table tb_t4
    -> (
    -> id int(11) primary key,
    -> name varchar(22),
    -> location varchar(50)
    -> );
Query OK, 0 rows affected (0.01 sec)

5.2.2 创建关联表

mysql> create table tb_tb
    -> (
    -> id int (11) primary key,
    -> name varchar(25),
    -> deptid int(11),
    -> salary float,
    -> constraint tb_tb_t4 foreign key(deptid) references tb_t4(id)
    -> );
Query OK, 0 rows affected (0.00 sec)

5.2.3 删除父表（tb_t4）

mysql> drop table tb_t4;
ERROR 1217 (23000): Cannot delete or update a parent row: a foreign key constraint fails

PS：可以看到在有外键约束时，主表不能直接删除

5.2.4 解除外键约束

mysql> alter table tb_tb drop  foreign key tb_tb_t4;
Query OK, 0 rows affected (0.00 sec)
Records: 0  Duplicates: 0  Warnings: 0

5.2.5 删除表

mysql> drop table tb_t4;
Query OK, 0 rows affected (0.01 sec)

猜你喜欢

转载自blog.csdn.net/weixin_45191791/article/details/111144923
今日推荐
《美国对全球网络空间安全与发展的威胁和破坏》报告发布
火速冲上 GitHub 热榜 —— 开源编程语言、框架哪有这么可爱？
北京人形机器人创新中心发布全球首个纯电驱拟人奔跑的全尺寸人形机器人“天工”
LFOSSA 源来如此公开课 | 掌握云原生未来：CNCF 认证全面攻略与备考秘籍
周排行
循环神经网络（rnn）讲解
Tigao教程四：单独的关节运动
金蝶K3WISE15.0-注册套打教程
如何在Mac上配置Kubernetes
Android应用结束自身进程的方法
SpringMVC学习 十三 拦截器栈
中国驻洛杉矶总领馆举行新春招待会
HttpClient get post 发送
11 - three.js 笔记 - 绘制三维字体模型
Mysql递归获取某个父节点下面的所有子节点和子节点上的所有父节点
每日归档
更多
2024-05-01(4)
2024-04-30(1)
2024-04-29(40)
2024-04-28(0)
2024-04-27(56)
2024-04-26(39)
2024-04-25(22)
2024-04-24(36)
2024-04-23(26)
2024-04-22(39)

代码天地 © 2018 codetd.com

境外服务器   最新电视剧2022