Java基础学习笔记二十五 MySQL
Posted 冰
tags:
篇首语：本文由小常识网(cha138.com)小编为大家整理，主要介绍了Java基础学习笔记二十五 MySQL相关的知识，希望对你有一定的参考价值。
mysql
在dos中操作mysql
连接mysql命令： mysql -uroot -p密码 ，连接OK，会出现mysql>
对数据库的操作
创建一个库
create database 库名 create database 库名 character set 编码
mysql> create database mybase; Query OK, 1 row affected (0.00 sec) mysql> show databases; +--------------------+ | Database | +--------------------+ | information_schema | | mybase | | mysql | | performance_schema | | test | +--------------------+ 5 rows in set (0.00 sec)
创建带有编码的
create database mybase01 character set gbk;
mysql> create database mybase01 character set gbk; Query OK, 1 row affected (0.00 sec) mysql> show databases; +--------------------+ | Database | +--------------------+ | information_schema | | mybase | | mybase01 | | mysql | | performance_schema | | test | +--------------------+ 6 rows in set (0.00 sec)
查看编码：
mysql> show create database mybase01; +----------+------------------------------------------------------------------+ | Database | Create Database | +----------+------------------------------------------------------------------+ | mybase01 | CREATE DATABASE `mybase01` /*!40100 DEFAULT CHARACTER SET gbk */ | +----------+------------------------------------------------------------------+ 1 row in set (0.00 sec)
查看数据库
mysql> show databases; +--------------------+ | Database | +--------------------+ | information_schema | | mybase | | mysql | | performance_schema | | test | +--------------------+ 5 rows in set (0.00 sec)
删除一个库
drop database 库名
mysql> drop database mybase; Query OK, 0 rows affected (0.00 sec) mysql> show databases; +--------------------+ | Database | +--------------------+ | information_schema | | mysql | | performance_schema | | test | +--------------------+ 4 rows in set (0.00 sec)
使用库 use 库名
mysql> use mybase Database changed
查看当前正在操作的库 select database();
mysql> select database(); +------------+ | database() | +------------+ | mybase | +------------+ 1 row in set (0.00 sec)
对数据库表的操作
创建一张表
创建数据表的格式 create table 表名( 列名1 数据类型 约束, 列名2 数据类型 约束, 列名3 数据类型 约束 );
/* 创建用户表,用户编号,姓名,用户的地址 将编号列,设置为主键约束,保证列的数据唯一性,非空性 primary key AUTO_INCREMENT 让主键列数据,实现自动增长 */ CREATE TABLE users ( uid INT PRIMARY KEY AUTO_INCREMENT , uname VARCHAR(20), uaddress VARCHAR(200) );
mysql> CREATE TABLE users ( -> uid INT PRIMARY KEY AUTO_INCREMENT , -> uname VARCHAR(20), -> uaddress VARCHAR(200) -> ); Query OK, 0 rows affected (0.02 sec)
查看数据库表 show tables;
mysql> show tables; +------------------+ | Tables_in_mybase | +------------------+ | users | +------------------+ 1 row in set (0.00 sec)
查看表的结构 desc 表名
mysql> desc users; +----------+--------------+------+-----+---------+----------------+ | Field | Type | Null | Key | Default | Extra | +----------+--------------+------+-----+---------+----------------+ | uid | int(11) | NO | PRI | NULL | auto_increment | | uname | varchar(20) | YES | | NULL | | | uaddress | varchar(200) | YES | | NULL | | +----------+--------------+------+-----+---------+----------------+ 3 rows in set (0.00 sec)
删除一张表 drop table 表名
mysql> drop table users； Query OK, 0 rows affected (0.00 sec) mysql> show tables; Empty set (0.00 sec)
修改表
添加一列 alter table 表名 add 字段名 类型(长度) [约束]
mysql> alter table users add tel int; Query OK, 0 rows affected (0.00 sec) Records: 0 Duplicates: 0 Warnings: 0
mysql> desc users ; +----------+--------------+------+-----+---------+----------------+ | Field | Type | Null | Key | Default | Extra | +----------+--------------+------+-----+---------+----------------+ | uid | int(11) | NO | PRI | NULL | auto_increment | | uname | varchar(20) | YES | | NULL | | | uaddress | varchar(200) | YES | | NULL | | | tel | int(11) | YES | | NULL | | +----------+--------------+------+-----+---------+----------------+ 4 rows in set (0.01 sec)
修改列的类型(长度、约束) alter table 表名 modify 要修改的字段名 类型(长度) [约束]
mysql> alter table users modify tel varchar(50); Query OK, 0 rows affected (0.27 sec) Records: 0 Duplicates: 0 Warnings: 0
修改列的列名 alter table 表名 change 旧列名 新列名 数据类型 约束
mysql> alter table users change tel newtel double; Query OK, 0 rows affected (0.01 sec) Records: 0 Duplicates: 0 Warnings: 0
mysql> desc users ; +----------+--------------+------+-----+---------+----------------+ | Field | Type | Null | Key | Default | Extra | +----------+--------------+------+-----+---------+----------------+ | uid | int(11) | NO | PRI | NULL | auto_increment | | uname | varchar(20) | YES | | NULL | | | uaddress | varchar(200) | YES | | NULL | | | newtel | double | YES | | NULL | | +----------+--------------+------+-----+---------+----------------+ 4 rows in set (0.00 sec)
删除表的列 alter table 表名 drop 列名
mysql> alter table users drop newtel; Query OK, 0 rows affected (0.02 sec) Records: 0 Duplicates: 0 Warnings: 0 mysql> desc users; +----------+--------------+------+-----+---------+----------------+ | Field | Type | Null | Key | Default | Extra | +----------+--------------+------+-----+---------+----------------+ | uid | int(11) | NO | PRI | NULL | auto_increment | | uname | varchar(20) | YES | | NULL | | | uaddress | varchar(200) | YES | | NULL | | +----------+--------------+------+-----+---------+----------------+ 3 rows in set (0.00 sec)
修改表名 rename table 表名 to 新表名
mysql> rename table users to newusers; Query OK, 0 rows affected (0.01 sec) mysql> show tables; +------------------+ | Tables_in_mybase | +------------------+ | newusers | +------------------+ 1 row in set (0.00 sec)
查看表的字符集编码 show create table newusers;
mysql> show create table newusers; +----------+-------------------------------------------------------------- -------------------------------------------------------------------------- -------------------------------------------------------+ | Table | Create Table | +----------+-------------------------------------------------------------- -------------------------------------------------------------------------- -------------------------------------------------------+ | newusers | CREATE TABLE `newusers` ( `uid` int(11) NOT NULL AUTO_INCREMENT, `uname` varchar(20) DEFAULT NULL, `uaddress` varchar(200) DEFAULT NULL, PRIMARY KEY (`uid`) ) ENGINE=InnoDB DEFAULT CHARSET=utf8 | +----------+-------------------------------------------------------------- -------------------------------------------------------------------------- -------------------------------------------------------+ 1 row in set (0.00 sec)
修改表的字符集 alter table 表名 character set 编码
mysql> alter table newusers character set gbk; Query OK, 0 rows affected (0.03 sec) Records: 0 Duplicates: 0 Warnings: 0 mysql> show create table newusers; +----------+------------------------------------------------------------------- ------------------------------------------------------------------------------- ------------------------------------------------------------------------------- ------------+ | Table | Create Table | +----------+------------------------------------------------------------------- ------------------------------------------------------------------------------- ------------------------------------------------------------------------------- ------------+ | newusers | CREATE TABLE `newusers` ( `uid` int(11) NOT NULL AUTO_INCREMENT, `uname` varchar(20) CHARACTER SET utf8 DEFAULT NULL, `uaddress` varchar(200) CHARACTER SET utf8 DEFAULT NULL, PRIMARY KEY (`uid`) ) ENGINE=InnoDB DEFAULT CHARSET=gbk | +----------+------------------------------------------------------------------- ------------------------------------------------------------------------------- ------------------------------------------------------------------------------- ------------+ 1 row in set (0.00 sec)
对数据库表记录进行操作(修改)
插入记录
insert into 表名(列名1,列名2,列名3……) values(值1,值2,值3……) insert into 表名 values(值1,值2,值3……)
insert into 表名 (列名1,列名2,列名3) values (值1,值2,值3),(值1,值2,值3)
先创建product表，然后添加数据。
CREATE TABLE product( -- 主键列,自动增长 id INT PRIMARY KEY AUTO_INCREMENT, -- 商品名字,可变字符,非空 pname VARCHAR(100) NOT NULL, -- 商品的价格,double price DOUBLE );
mysql> INSERT INTO product (id,pname,price) VALUES (1,\'笔记本\',5555.99); ERROR 1366 (HY000): Incorrect string value: \'\\xB1\\xCA\\xBC\\xC7\\xB1\\xBE\' for column \'pname\' at row 1 mysql> INSERT INTO product (id,pname,price) VALUES (2,\'智能手机\',9999); ERROR 1366 (HY000): Incorrect string value: \'\\xD6\\xC7\\xC4\\xDC\\xCA\\xD6...\' for column \'pname\' at row 1 mysql> INSERT INTO product (id,pname,price) VALUES (1,\'computer\',5555.99); Query OK, 1 row affected (0.00 sec) mysql> INSERT INTO product (id,pname,price) VALUES (1,\'phone\',5555.99); ERROR 1062 (23000): Duplicate entry \'1\' for key \'PRIMARY\' mysql> INSERT INTO product (id,pname,price) VALUES (2,\'phone\',5555.99); Query OK, 1 row affected (0.00 sec)
插入数据中文乱码问题解决办法
乱码原因：客户端和服务器之间传递字符的编码规则不一样。
方式一：直接修改数据库安装目录里面的my.ini文件的第57行【不建议】
方式二： set names gbk;
mysql> set names gbk; Query OK, 0 rows affected (0.00 sec)
再次插入中文，可以看到，不报错了。
mysql> INSERT INTO product (id,pname,price) VALUES (3,\'笔记本\',5555.99); Query OK, 1 row affected (0.00 sec) mysql> INSERT INTO product (id,pname,price) VALUES (4,\'智能手机\',9999); Query OK, 1 row affected (0.00 sec)
添加数据格式,不考虑主键 insert into 表名 (列名) values (值)
mysql> INSERT INTO product (pname,price) VALUES(\'洗衣机\',800); Query OK, 1 row affected (0.00 sec)
添加数据格式,所有值全给出 insert into 表名 values (全列值)
mysql> INSERT INTO product VALUES (6,\'微波炉\',300.25); Query OK, 1 row affected (0.00 sec)
添加数据格式,批量写入 insert into 表名 (列名1,列名2,列名3) values (值1,值2,值3),(值1,值2,值3)
mysql> INSERT INTO product (pname,price) VALUES -> (\'智能机器人\',25999.22), -> (\'彩色电视\',1250.36), -> (\'沙发\',5899.02); Query OK, 3 rows affected (0.00 sec) Records: 3 Duplicates: 0 Warnings: 0
修改表记录
先看看表中的所有数据：
mysql> select * from product; +----+------------+----------+ | id | pname | price | +----+------------+----------+ | 1 | computer | <以上是关于Java基础学习笔记二十五 MySQL的主要内容，如果未能解决你的问题，请参考以下文章