Mysql简明语法

show databases ;
use mybatis;
show tables ;
select * from user;
select * from user where id=1;
update user set name="酷安" , pwd ="123456" where id=1;
insert  user(id,name,pwd) values (3,"小美","xxxccc");
delete from user where name="tomcat";
ALTER TABLE table_name ADD COLUMN id int(30) NOT NULL;
ALTER TABLE table_name DROP COLUMN ...

SELECT [field1, field12, ..., ] fun_name
FROM tablename
JOIN  ON join_condition
WHERE where_conditon
GROUP BY field1, field12, ..., fieldn
[WITH ROLLUP]
[HAVING having_condition]
ORDER BY field1, field12, ..., fieldn [ASC | DESC]]

外键：

ALTER TABLE 子表 ADD CONSTRAINT 外键名 FOREIGN KEY(子表字段）REFERENCES主表(主表字段);

ALTER TABLE 子表 DROP FOREIGN KEY 外键名