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设置数据库字符集
set character_set_database =utf8;
命令行进入MySQL：
Enter password: **** Welcome to the MySQL monitor. Commands end with ; or \g. Your MySQL connection id is 104 Server version: 5.7.26-log MySQL Community Server (GPL) Copyright (c) 2000, 2019, Oracle and/or its affiliates. All rights reserved. Oracle is a registered trademark of Oracle Corporation and/or its affiliates. Other names may be trademarks of their respective owners. Type 'help;' or '\h' for help. Type '\c' to clear the current input statement. //查看数据库 mysql> show databases; +--------------------+ | Database | +--------------------+ | information_schema | | mysql | | performance_schema | | sys | +--------------------+ 5 rows in set (0.00 sec) 注意：这些数据库不要删了，有涉及到数据库的配置信息 //创建数据库users mysql> create database users; mysql> show databases; +--------------------+ | Database | +--------------------+ | information_schema | | mysql | | performance_schema | | sys | | users | +--------------------+ 5 rows in set (0.28 sec) //查看数据库定义语句 mysql> show create database users; +----------+----------------------------------------------------------------+ | Database | Create Database | +----------+----------------------------------------------------------------+ | users | CREATE DATABASE `users` /*!40100 DEFAULT CHARACTER SET utf8 */ | +----------+----------------------------------------------------------------+ 1 row in set (0.00 sec) //删除数据库 drop database users; //切换数据库 mysql> use users Database changed //查看当前正在使用的数据库 mysql> select database(); +------------+ | database() | +------------+ | users | +------------+ 1 row in set (0.00 sec) //在users数据库创建user表 mysql> create table user( id int not null AUTO_INCREMENT, name varchar(10) not null, age int ); //查看表定义语句 mysql> show create table user; +-------+---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+ | Table | Create Table | +-------+---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+ | user | CREATE TABLE `user` ( `id` int(11) NOT NULL AUTO_INCREMENT, `name` varchar(20) CHARACTER SET utf8 DEFAULT NULL, `age` int(11) DEFAULT NULL, PRIMARY KEY (`id`) ) ENGINE=InnoDB AUTO_INCREMENT=14 DEFAULT CHARSET=latin1 | +-------+---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+ 1 row in set (0.00 sec) //查看表结构 mysql> desc user; +-------+-------------+------+-----+---------+----------------+ | Field | Type | Null | Key | Default | Extra | +-------+-------------+------+-----+---------+----------------+ | id | int(11) | NO | PRI | NULL | auto_increment | | name | varchar(20) | YES | | NULL | | | age | int(11) | YES | | NULL | | +-------+-------------+------+-----+---------+----------------+ 3 rows in set (0.00 sec) //插入信息 mysql>insert into user values(null,'王五','28'); OR insert into user (name,age) valuse('李四','28'); //解释查询过程 mysql> explain select * from user; +----+-------------+-------+------------+------+---------------+------+---------+------+------+----------+-------+ | id | select_type | table | partitions | type | possible_keys | key | key_len | ref | rows | filtered | Extra | +----+-------------+-------+------------+------+---------------+------+---------+------+------+----------+-------+ | 1 | SIMPLE | user | NULL | ALL | NULL | NULL | NULL | NULL | 6 | 100.00 | NULL | +----+-------------+-------+------------+------+---------------+------+---------+------+------+----------+-------+ 1 row in set, 1 warning (0.00 sec) mysql> explain select * from user where id=1; +----+-------------+-------+------------+-------+---------------+---------+---------+-------+------+----------+-------+ | id | select_type | table | partitions | type | possible_keys | key | key_len | ref | rows | filtered | Extra | +----+-------------+-------+------------+-------+---------------+---------+---------+-------+------+----------+-------+ | 1 | SIMPLE | user | NULL | const | PRIMARY | PRIMARY | 4 | const | 1 | 100.00 | NULL | +----+-------------+-------+------------+-------+---------------+---------+---------+-------+------+----------+-------+ 1 row in set, 1 warning (0.00 sec) //更改数据库字符集 mysql> ALTER DATABASE users DEFAULT CHARACTER SET='utf8'; Query OK, 1 row affected (0.00 sec) mysql> insert into user values(null,'王五','28'); Query OK, 1 row affected, 1 warning (0.30 sec) mysql> insert into user (name,age) values('admin',18); Query OK, 1 row affected (0.08 sec) mysql> select * from user; +----+-------+------+ | id | name | age | +----+-------+------+ | 1 | 王五 | 28 | | 2 | admin | 18 | +----+-------+------+ 2 rows in set (0.00 sec) mysql>字符集问题 mysql> insert into user values(null,‘王鹏’,‘24’); Query OK, 1 row affected, 1 warning (0.30 sec)
mysql> select * from user; ±—±------±-----+ | id | name | age | ±—±------±-----+ | 1 | ??? | 24 | ±—±------±-----+ 1 rows in set (0.00 sec)
由于插入中文导致乱码 //更改数据库字符集 mysql> ALTER DATABASE users DEFAULT CHARACTER SET=‘utf8’;MySQL数据类型
Java数据类型MySQL数据类型intintchar/stringchar [固定长度]/varchar [可变长度]doubledoublefloatfloatbooleanbooleandatedate [YYYY-MM-DD]time [ hh:mm:ss]datetime [YYYY-MM-DD hh:mm:ss] 默认值NULLtimestamp [YYYY-MM-DD hh:mm:ss] 默认当前时间text 存放文本blob 存放二进制