MYSQL中的查询

一、创建索引

create table student(
  sid int primary key,
  card_id varchar(20), 
  name varchar(20),
	gender varchar(20), 
	age int,
	birth date,
  phone_num varchar(20), 
	score double,
  index index_name(name) -- 给name列创建索引
);
select * from student where name ='张三';

2.直接创建：

create index index_gender on student(gender);

3.修改表结构添加索引

alter table student add index index_age(age);

– 查看索引：