sql基础

create table 

drop table   if exists user;

create table user(
	id int primary key not null,
	birday date,
	name varchar(30) not null,
	phone int,
	address varchar(255),
	sex char
);

 最后一列不要","号，varchar要指定长度。

 

insert into

 

insert into user values
(1382,'2000-10-10','jack',123,'sdf','M' ),
(1823,'2000-10-10','jack',123,'sdf' ,'M' ),
(1673,'2000-10-10','sfdfs',123,'sdf' ,'M' ),
(1453,'2000-10-10','jack',123,'sdf','F'  );

 

 多条数据同时插入，mysql有效其他未知；

 

limit:

 

select * from user limit 0 ,2;

 

 limit参数用","隔开

 

alter add

 

alter table user 
add type char(1)

 

 

alter drop

alter table user

drop column sex;

 指定 column

 

alter modify

 

alter table 
modify sex char(2)

 

 modify 对mysql有效，另有 

 

alter table user
alter column sex char(2)

 

 

create index:

 

create index name_index on user (name);

 name_index 不要单引号。

 

drop index

 

drop index name_index

 不能修改index，只能删除在添加