建库：
create database db_name character set =utf8;
/*建立库db_name，默认字符集为utf8*/

建表：
create table tb_1 (id int auto_increment primary key, remark varchar(20)) engine=innodb default character set=utf8 auto_increment =100;
/*建立表tb_1，存储引擎为innodb,默认字符集为utf8，自增列开始值为100*/

create table tb_2 (id2 int auto_increment primary key, remark varchar(20)) engine=innodb default character set=utf8 auto_increment =100;

删表
DROP TABLE IF EXISTS `A`;

删库
drop database 库1

内联接：
select * from t1 inner join t2 where t1.id=t2.id2;

左联接：
select * from t1 left join t2 on t1.id=t2.id2;

右联接：
select * from t1 right join t2 on t1.id=t2.id2;

全联接：
select * from t1,t2 

导出数据表数据
mysqldump -uroot -p ugood_newspaper_db merchant_orders>aaa.sql;
ugood_newspaper_db数据库名，merchant_orders表名，aaa是导出文件名