基本的sql语句

创建数据库：create database mydemo;
删除数据库：drop database mydemo;
设置数据库编码：alter database mydemo character set utf8;
显示当前数据编码：show variables like 'character_set_database';
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创建数据表：create table demotable(id int primary key auto_increment,name varchar(255) not null,sex enum('m','w'),content text,cretime date);
数据表添加字段：alter table demotable add column age int(3);
删除表中某个字段：ALTER TABLE demotable DROP COLUMN age;
添加数据：insert into demotable values('','Tom','m','helloworld','1232134'),('','Joan','w','yes','2132131');
设置某一个字段为空：update demotable set  content=null;
清空表中的数据：delete  from demotable ;
清除满足条件的语句：delete  from demotable where id=1;
查看数据：select * from demotable;
查看表属性（包括字段类型默认值。。）：desc demotable;
设置表中某个字段的编码：ALTER TABLE demotable CHANGE name name VARCHAR(36) CHARACTER SET utf8 NOT NULL;